diff --git a/frontend/src/components/application-loader/application-loader.tsx b/frontend/src/components/application-loader/application-loader.tsx
index 3c0062e0c..aa9161216 100644
--- a/frontend/src/components/application-loader/application-loader.tsx
+++ b/frontend/src/components/application-loader/application-loader.tsx
@@ -42,6 +42,8 @@ export const ApplicationLoader: React.FC<PropsWithChildren> = ({ children }) =>
           For further information look into the browser console.
         </Fragment>
       )
+    } else {
+      return null
     }
   }, [error])
 
diff --git a/frontend/src/components/application-loader/loading-screen/loading-screen.tsx b/frontend/src/components/application-loader/loading-screen/loading-screen.tsx
index fb274dc93..c19944370 100644
--- a/frontend/src/components/application-loader/loading-screen/loading-screen.tsx
+++ b/frontend/src/components/application-loader/loading-screen/loading-screen.tsx
@@ -11,7 +11,7 @@ import React from 'react'
 import { Alert } from 'react-bootstrap'
 
 export interface LoadingScreenProps {
-  errorMessage?: string | ReactElement
+  errorMessage?: string | ReactElement | null
 }
 
 /**
diff --git a/frontend/src/components/common/highlighted-code/hooks/use-attach-line-numbers.tsx b/frontend/src/components/common/highlighted-code/hooks/use-attach-line-numbers.tsx
index 75eceb388..42ef0b15a 100644
--- a/frontend/src/components/common/highlighted-code/hooks/use-attach-line-numbers.tsx
+++ b/frontend/src/components/common/highlighted-code/hooks/use-attach-line-numbers.tsx
@@ -14,21 +14,21 @@ import { Fragment, useMemo } from 'react'
  * @param lines The elements to wrap
  * @param startLineNumber The line number to start with. Will default to 1 if omitted.
  */
-export const useAttachLineNumbers = (
-  lines: undefined | ReactElement[],
-  startLineNumber = 1
-): undefined | ReactElement[] =>
-  useMemo(
-    () =>
-      lines?.map((line, index) => (
-        <Fragment key={index}>
-          <span {...cypressId('linenumber')} className={styles['linenumber']}>
-            {startLineNumber + index}
-          </span>
-          <div {...cypressId('codeline')} className={styles['codeline']}>
-            {line}
-          </div>
-        </Fragment>
-      )),
-    [startLineNumber, lines]
-  )
+export const useAttachLineNumbers = (lines: ReactElement[] | null, startLineNumber = 1): ReactElement | null => {
+  return useMemo(() => {
+    if (lines === null) {
+      return null
+    }
+    const adjustedLines = lines.map((line, index) => (
+      <Fragment key={index}>
+        <span {...cypressId('linenumber')} className={styles['linenumber']}>
+          {startLineNumber + index}
+        </span>
+        <div {...cypressId('codeline')} className={styles['codeline']}>
+          {line}
+        </div>
+      </Fragment>
+    ))
+    return <Fragment>{adjustedLines}</Fragment>
+  }, [startLineNumber, lines])
+}
diff --git a/frontend/src/components/common/highlighted-code/hooks/use-code-dom.tsx b/frontend/src/components/common/highlighted-code/hooks/use-code-dom.tsx
index 17dc3f24e..6b8000f2e 100644
--- a/frontend/src/components/common/highlighted-code/hooks/use-code-dom.tsx
+++ b/frontend/src/components/common/highlighted-code/hooks/use-code-dom.tsx
@@ -3,7 +3,7 @@
  *
  * SPDX-License-Identifier: AGPL-3.0-only
  */
-import { HtmlToReact } from '../../../../components/common/html-to-react/html-to-react'
+import { HtmlToReact } from '../../html-to-react/html-to-react'
 import type { HLJSApi } from 'highlight.js'
 import type { ReactElement } from 'react'
 import React, { useMemo } from 'react'
@@ -16,10 +16,10 @@ import React, { useMemo } from 'react'
  * @param language The language of the code to use for highlighting
  * @return The react elements that represent the highlighted code
  */
-export const useCodeDom = (code: string, hljs: HLJSApi | undefined, language?: string): ReactElement[] | undefined => {
+export const useCodeDom = (code: string, hljs: HLJSApi | undefined, language?: string): ReactElement[] | null => {
   return useMemo(() => {
     if (!hljs) {
-      return
+      return null
     }
     if (!!language && hljs.listLanguages().includes(language)) {
       const highlightedHtml = hljs.highlight(code, { language }).value
diff --git a/frontend/src/components/common/renderer-iframe/hooks/use-send-additional-configuration-to-renderer.ts b/frontend/src/components/common/renderer-iframe/hooks/use-send-additional-configuration-to-renderer.ts
index c4428c79c..68fc253db 100644
--- a/frontend/src/components/common/renderer-iframe/hooks/use-send-additional-configuration-to-renderer.ts
+++ b/frontend/src/components/common/renderer-iframe/hooks/use-send-additional-configuration-to-renderer.ts
@@ -20,7 +20,7 @@ export const useSendAdditionalConfigurationToRenderer = (rendererReady: boolean)
   useSendToRenderer(
     useMemo(() => {
       return newlinesAreBreaks === undefined
-        ? undefined
+        ? null
         : {
             type: CommunicationMessageType.SET_ADDITIONAL_CONFIGURATION,
             darkModePreference: darkModePreference,
diff --git a/frontend/src/components/common/renderer-iframe/hooks/use-send-scroll-state.ts b/frontend/src/components/common/renderer-iframe/hooks/use-send-scroll-state.ts
index a6f1925c1..7936c00c2 100644
--- a/frontend/src/components/common/renderer-iframe/hooks/use-send-scroll-state.ts
+++ b/frontend/src/components/common/renderer-iframe/hooks/use-send-scroll-state.ts
@@ -15,13 +15,13 @@ import { useMemo, useRef } from 'react'
  * @param scrollState The scroll state to send
  * @param rendererReady Defines if the target renderer is ready
  */
-export const useSendScrollState = (scrollState: ScrollState | undefined, rendererReady: boolean): void => {
+export const useSendScrollState = (scrollState: ScrollState | null, rendererReady: boolean): void => {
   const oldScrollState = useRef<ScrollState | undefined>(undefined)
 
   useSendToRenderer(
     useMemo(() => {
       if (!scrollState || equal(scrollState, oldScrollState.current)) {
-        return
+        return null
       }
       oldScrollState.current = scrollState
       return { type: CommunicationMessageType.SET_SCROLL_STATE, scrollState }
diff --git a/frontend/src/components/common/renderer-iframe/renderer-iframe.tsx b/frontend/src/components/common/renderer-iframe/renderer-iframe.tsx
index a7fa837e3..abe822be6 100644
--- a/frontend/src/components/common/renderer-iframe/renderer-iframe.tsx
+++ b/frontend/src/components/common/renderer-iframe/renderer-iframe.tsx
@@ -112,7 +112,7 @@ export const RendererIframe: React.FC<RendererIframeProps> = ({
     CommunicationMessageType.EXTENSION_EVENT,
     useMemo(() => {
       return eventEmitter === undefined
-        ? undefined
+        ? null
         : (values: ExtensionEvent) => eventEmitter.emit(values.eventName, values.payload)
     }, [eventEmitter])
   )
@@ -159,7 +159,7 @@ export const RendererIframe: React.FC<RendererIframeProps> = ({
   useSendAdditionalConfigurationToRenderer(rendererReady)
   useSendMarkdownToRenderer(markdownContentLines, rendererReady)
 
-  useSendScrollState(scrollState, rendererReady)
+  useSendScrollState(scrollState ?? null, rendererReady)
   useEditorReceiveHandler(
     CommunicationMessageType.SET_SCROLL_STATE,
     useCallback((values: SetScrollStateMessage) => onScroll?.(values.scrollState), [onScroll])
diff --git a/frontend/src/components/editor-page/change-content-context/use-change-editor-content-callback.tsx b/frontend/src/components/editor-page/change-content-context/use-change-editor-content-callback.tsx
index 14909852c..18565a5b4 100644
--- a/frontend/src/components/editor-page/change-content-context/use-change-editor-content-callback.tsx
+++ b/frontend/src/components/editor-page/change-content-context/use-change-editor-content-callback.tsx
@@ -40,9 +40,7 @@ export const changeEditorContent = (view: EditorView, formatter: ContentFormatte
 export const useChangeEditorContentCallback = () => {
   const [codeMirrorRef] = useCodemirrorReferenceContext()
   return useMemo(() => {
-    if (codeMirrorRef) {
-      return (callback: ContentFormatter) => changeEditorContent(codeMirrorRef, callback)
-    }
+    return !codeMirrorRef ? null : (callback: ContentFormatter) => changeEditorContent(codeMirrorRef, callback)
   }, [codeMirrorRef])
 }
 
diff --git a/frontend/src/components/editor-page/editor-pane/editor-pane.tsx b/frontend/src/components/editor-page/editor-pane/editor-pane.tsx
index 44bf89fac..90226d11e 100644
--- a/frontend/src/components/editor-page/editor-pane/editor-pane.tsx
+++ b/frontend/src/components/editor-page/editor-pane/editor-pane.tsx
@@ -59,14 +59,14 @@ export type EditorPaneProps = ScrollProps
  */
 export const EditorPane: React.FC<EditorPaneProps> = ({ scrollState, onScroll, onMakeScrollSource }) => {
   const { dispatchUiNotification } = useUiNotifications()
-  useApplyScrollState(scrollState)
+  useApplyScrollState(scrollState ?? null)
 
   const messageTransporter = useRealtimeConnection()
 
   useDisconnectOnUserLoginStatusChange(messageTransporter)
 
   const realtimeDoc = useRealtimeDoc()
-  const editorScrollExtension = useCodeMirrorScrollWatchExtension(onScroll)
+  const editorScrollExtension = useCodeMirrorScrollWatchExtension(onScroll ?? null)
   const tablePasteExtensions = useCodeMirrorTablePasteExtension()
   const fileInsertExtension = useCodeMirrorFileInsertExtension()
   const spellCheckExtension = useCodeMirrorSpellCheckExtension()
diff --git a/frontend/src/components/editor-page/editor-pane/hooks/codemirror-extensions/use-code-mirror-scroll-watch-extension.ts b/frontend/src/components/editor-page/editor-pane/hooks/codemirror-extensions/use-code-mirror-scroll-watch-extension.ts
index b0a32e4d4..79261b90f 100644
--- a/frontend/src/components/editor-page/editor-pane/hooks/codemirror-extensions/use-code-mirror-scroll-watch-extension.ts
+++ b/frontend/src/components/editor-page/editor-pane/hooks/codemirror-extensions/use-code-mirror-scroll-watch-extension.ts
@@ -35,7 +35,7 @@ export const extractScrollState = (view: EditorView): ScrollState => {
  * @param onScroll The callback that is used to post {@link ScrollState scroll states} when the editor view is scrolling.
  * @return The extensions that watches the scrolling in the editor.
  */
-export const useCodeMirrorScrollWatchExtension = (onScroll: OnScrollCallback): Extension => {
+export const useCodeMirrorScrollWatchExtension = (onScroll: OnScrollCallback | null): Extension => {
   const onEditorScroll = useCallback(
     (view: EditorView) => {
       if (!onScroll || !view) {
diff --git a/frontend/src/components/editor-page/editor-pane/hooks/use-apply-scroll-state.ts b/frontend/src/components/editor-page/editor-pane/hooks/use-apply-scroll-state.ts
index d36f646d2..6e9c87e8e 100644
--- a/frontend/src/components/editor-page/editor-pane/hooks/use-apply-scroll-state.ts
+++ b/frontend/src/components/editor-page/editor-pane/hooks/use-apply-scroll-state.ts
@@ -35,7 +35,7 @@ const applyScrollState = (view: EditorView, scrollState: ScrollState): void => {
  *
  * @param scrollState The scroll state that should be monitored
  */
-export const useApplyScrollState = (scrollState?: ScrollState): void => {
+export const useApplyScrollState = (scrollState: ScrollState | null): void => {
   const lastScrollPosition = useRef<ScrollState>()
   const [codeMirrorRef] = useCodemirrorReferenceContext()
 
diff --git a/frontend/src/components/editor-page/editor-pane/hooks/use-line-based-position.ts b/frontend/src/components/editor-page/editor-pane/hooks/use-line-based-position.ts
index 09bf2b0a4..987451bd1 100644
--- a/frontend/src/components/editor-page/editor-pane/hooks/use-line-based-position.ts
+++ b/frontend/src/components/editor-page/editor-pane/hooks/use-line-based-position.ts
@@ -23,13 +23,13 @@ const calculateLineBasedPosition = (absolutePosition: number, lineStartIndexes:
 /**
  * Returns the line+character based position of the to-cursor, if available.
  */
-export const useLineBasedToPosition = (): LineBasedPosition | undefined => {
+export const useLineBasedToPosition = (): LineBasedPosition | null => {
   const lineStartIndexes = useApplicationState((state) => state.noteDetails?.markdownContent.lineStartIndexes ?? [])
   const selectionTo = useApplicationState((state) => state.noteDetails?.selection.to)
 
   return useMemo(() => {
     if (selectionTo === undefined) {
-      return undefined
+      return null
     }
     return calculateLineBasedPosition(selectionTo, lineStartIndexes)
   }, [selectionTo, lineStartIndexes])
diff --git a/frontend/src/components/editor-page/editor-pane/hooks/yjs/use-websocket-url.ts b/frontend/src/components/editor-page/editor-pane/hooks/yjs/use-websocket-url.ts
index 6ce35d265..0f514e8f8 100644
--- a/frontend/src/components/editor-page/editor-pane/hooks/yjs/use-websocket-url.ts
+++ b/frontend/src/components/editor-page/editor-pane/hooks/yjs/use-websocket-url.ts
@@ -13,7 +13,7 @@ const LOCAL_FALLBACK_URL = 'ws://localhost:8080/realtime/'
 /**
  * Provides the URL for the realtime endpoint.
  */
-export const useWebsocketUrl = (): URL | undefined => {
+export const useWebsocketUrl = (): URL | null => {
   const noteId = useApplicationState((state) => state.noteDetails?.id)
   const baseUrl = useBaseUrl()
 
@@ -34,7 +34,7 @@ export const useWebsocketUrl = (): URL | undefined => {
 
   return useMemo(() => {
     if (noteId === '' || noteId === undefined) {
-      return
+      return null
     }
     const url = new URL(websocketUrl)
     url.search = `?noteId=${noteId}`
diff --git a/frontend/src/components/editor-page/editor-pane/status-bar/selected-characters.tsx b/frontend/src/components/editor-page/editor-pane/status-bar/selected-characters.tsx
index f57fe10ac..46df11751 100644
--- a/frontend/src/components/editor-page/editor-pane/status-bar/selected-characters.tsx
+++ b/frontend/src/components/editor-page/editor-pane/status-bar/selected-characters.tsx
@@ -16,7 +16,7 @@ export const SelectedCharacters: React.FC = () => {
 
   const selection = useApplicationState((state) => state.noteDetails?.selection)
   const count = useMemo(
-    () => (selection === undefined || selection.to === undefined ? undefined : selection.to - selection.from),
+    () => (selection === undefined || selection.to === undefined ? null : selection.to - selection.from),
     [selection]
   )
   const countTranslationOptions = useMemo(() => ({ count }), [count])
diff --git a/frontend/src/components/editor-page/editor-pane/tool-bar/table-picker/table-size-text.tsx b/frontend/src/components/editor-page/editor-pane/tool-bar/table-picker/table-size-text.tsx
index a5219ef57..aa966d129 100644
--- a/frontend/src/components/editor-page/editor-pane/tool-bar/table-picker/table-size-text.tsx
+++ b/frontend/src/components/editor-page/editor-pane/tool-bar/table-picker/table-size-text.tsx
@@ -20,7 +20,7 @@ export const TableSizeText: React.FC<TableSizeProps> = ({ tableSize }) => {
   useTranslation()
 
   const translationValues = useMemo(() => {
-    return tableSize ? { cols: tableSize.columns, rows: tableSize.rows } : undefined
+    return tableSize ? { cols: tableSize.columns, rows: tableSize.rows } : null
   }, [tableSize])
 
   if (!translationValues) {
diff --git a/frontend/src/components/editor-page/renderer-pane/hooks/use-on-scroll-with-line-offset.ts b/frontend/src/components/editor-page/renderer-pane/hooks/use-on-scroll-with-line-offset.ts
index 279b3af22..294d3f9c9 100644
--- a/frontend/src/components/editor-page/renderer-pane/hooks/use-on-scroll-with-line-offset.ts
+++ b/frontend/src/components/editor-page/renderer-pane/hooks/use-on-scroll-with-line-offset.ts
@@ -13,15 +13,15 @@ import { useMemo } from 'react'
  * @param onScroll The callback that posts a scroll state
  * @return the modified callback that posts the same scroll state but with line offset
  */
-export const useOnScrollWithLineOffset = (onScroll: ScrollCallback | undefined): ScrollCallback | undefined => {
+export const useOnScrollWithLineOffset = (onScroll: ScrollCallback | null): ScrollCallback | null => {
   return useMemo(() => {
-    if (onScroll === undefined) {
-      return undefined
+    if (onScroll === null) {
+      return null
     } else {
       return (scrollState: ScrollState) => {
         const noteDetails = getGlobalState().noteDetails
         if (noteDetails === null) {
-          return undefined
+          return null
         }
         onScroll({
           firstLineInView: scrollState.firstLineInView + noteDetails.startOfContentLineOffset,
diff --git a/frontend/src/components/editor-page/renderer-pane/hooks/use-scroll-state-without-line-offset.ts b/frontend/src/components/editor-page/renderer-pane/hooks/use-scroll-state-without-line-offset.ts
index 777fc4ba3..ebdd37a3a 100644
--- a/frontend/src/components/editor-page/renderer-pane/hooks/use-scroll-state-without-line-offset.ts
+++ b/frontend/src/components/editor-page/renderer-pane/hooks/use-scroll-state-without-line-offset.ts
@@ -13,11 +13,11 @@ import { useMemo } from 'react'
  * @param scrollState The original scroll state with the line offset
  * @return the adjusted scroll state without the line offset
  */
-export const useScrollStateWithoutLineOffset = (scrollState: ScrollState | undefined): ScrollState | undefined => {
+export const useScrollStateWithoutLineOffset = (scrollState: ScrollState | null): ScrollState | null => {
   const lineOffset = useApplicationState((state) => state.noteDetails?.startOfContentLineOffset)
   return useMemo(() => {
-    return scrollState === undefined || lineOffset === undefined
-      ? undefined
+    return scrollState === null || lineOffset === undefined
+      ? null
       : {
           firstLineInView: scrollState.firstLineInView - lineOffset,
           scrolledPercentage: scrollState.scrolledPercentage
diff --git a/frontend/src/components/editor-page/renderer-pane/renderer-pane.tsx b/frontend/src/components/editor-page/renderer-pane/renderer-pane.tsx
index 75f0ec398..ce2c41342 100644
--- a/frontend/src/components/editor-page/renderer-pane/renderer-pane.tsx
+++ b/frontend/src/components/editor-page/renderer-pane/renderer-pane.tsx
@@ -29,8 +29,8 @@ export type RendererPaneProps = Omit<
 export const RendererPane: React.FC<RendererPaneProps> = ({ scrollState, onScroll, ...props }) => {
   const trimmedContentLines = useTrimmedNoteMarkdownContentWithoutFrontmatter()
   const noteType = useApplicationState((state) => state.noteDetails?.frontmatter.type)
-  const adjustedOnScroll = useOnScrollWithLineOffset(onScroll)
-  const adjustedScrollState = useScrollStateWithoutLineOffset(scrollState)
+  const adjustedOnScroll = useOnScrollWithLineOffset(onScroll ?? null)
+  const adjustedScrollState = useScrollStateWithoutLineOffset(scrollState ?? null)
 
   if (!noteType) {
     return null
diff --git a/frontend/src/components/editor-page/sidebar/specific-sidebar-entries/note-info-sidebar-menu/note-info-line/note-info-line-created-at.tsx b/frontend/src/components/editor-page/sidebar/specific-sidebar-entries/note-info-sidebar-menu/note-info-line/note-info-line-created-at.tsx
index f9be610d0..d39b6c794 100644
--- a/frontend/src/components/editor-page/sidebar/specific-sidebar-entries/note-info-sidebar-menu/note-info-line/note-info-line-created-at.tsx
+++ b/frontend/src/components/editor-page/sidebar/specific-sidebar-entries/note-info-sidebar-menu/note-info-line/note-info-line-created-at.tsx
@@ -18,7 +18,7 @@ export const NoteInfoLineCreatedAt: React.FC = () => {
   useTranslation()
   const noteCreateTime = useApplicationState((state) => state.noteDetails?.createdAt)
   const noteCreateDateTime = useMemo(
-    () => (noteCreateTime === undefined ? undefined : DateTime.fromSeconds(noteCreateTime)),
+    () => (noteCreateTime === undefined ? null : DateTime.fromSeconds(noteCreateTime)),
     [noteCreateTime]
   )
 
diff --git a/frontend/src/components/editor-page/sidebar/specific-sidebar-entries/note-info-sidebar-menu/note-info-line/note-info-line-updated-at.tsx b/frontend/src/components/editor-page/sidebar/specific-sidebar-entries/note-info-sidebar-menu/note-info-line/note-info-line-updated-at.tsx
index 85251a40a..b275aa572 100644
--- a/frontend/src/components/editor-page/sidebar/specific-sidebar-entries/note-info-sidebar-menu/note-info-line/note-info-line-updated-at.tsx
+++ b/frontend/src/components/editor-page/sidebar/specific-sidebar-entries/note-info-sidebar-menu/note-info-line/note-info-line-updated-at.tsx
@@ -18,7 +18,7 @@ export const NoteInfoLineUpdatedAt: React.FC = () => {
   useTranslation()
   const noteUpdateTime = useApplicationState((state) => state.noteDetails?.updatedAt)
   const noteUpdateDateTime = useMemo(
-    () => (noteUpdateTime === undefined ? undefined : DateTime.fromSeconds(noteUpdateTime)),
+    () => (noteUpdateTime === undefined ? null : DateTime.fromSeconds(noteUpdateTime)),
     [noteUpdateTime]
   )
 
diff --git a/frontend/src/components/editor-page/sidebar/specific-sidebar-entries/permissions-sidebar-entry/permissions-modal/permission-entry-user.tsx b/frontend/src/components/editor-page/sidebar/specific-sidebar-entries/permissions-sidebar-entry/permissions-modal/permission-entry-user.tsx
index 02ff3e8c2..f960a014b 100644
--- a/frontend/src/components/editor-page/sidebar/specific-sidebar-entries/permissions-sidebar-entry/permissions-modal/permission-entry-user.tsx
+++ b/frontend/src/components/editor-page/sidebar/specific-sidebar-entries/permissions-sidebar-entry/permissions-modal/permission-entry-user.tsx
@@ -40,8 +40,8 @@ export const PermissionEntryUser: React.FC<PermissionEntryUserProps & Permission
 
   const permissionInconsistent = useMemo(
     () =>
-      (everyonePermission && everyonePermission.canEdit && !entry.canEdit) ||
-      (loggedInPermission && loggedInPermission.canEdit && !entry.canEdit),
+      (!!everyonePermission && everyonePermission.canEdit && !entry.canEdit) ||
+      (!!loggedInPermission && loggedInPermission.canEdit && !entry.canEdit),
     [everyonePermission, loggedInPermission, entry]
   )
 
diff --git a/frontend/src/components/editor-page/sidebar/specific-sidebar-entries/share-note-sidebar-entry/share-modal/note-url-field.tsx b/frontend/src/components/editor-page/sidebar/specific-sidebar-entries/share-note-sidebar-entry/share-modal/note-url-field.tsx
index 70fcd03fb..1150791ba 100644
--- a/frontend/src/components/editor-page/sidebar/specific-sidebar-entries/share-note-sidebar-entry/share-modal/note-url-field.tsx
+++ b/frontend/src/components/editor-page/sidebar/specific-sidebar-entries/share-note-sidebar-entry/share-modal/note-url-field.tsx
@@ -28,7 +28,7 @@ export const NoteUrlField: React.FC<LinkFieldProps> = ({ type }) => {
 
   const url = useMemo(() => {
     if (noteId === undefined) {
-      return undefined
+      return null
     }
     const url = new URL(baseUrl)
     url.pathname += `${type}/${noteId}`
diff --git a/frontend/src/components/editor-page/synced-scroll/scroll-props.ts b/frontend/src/components/editor-page/synced-scroll/scroll-props.ts
index 2b07e527d..07608abbb 100644
--- a/frontend/src/components/editor-page/synced-scroll/scroll-props.ts
+++ b/frontend/src/components/editor-page/synced-scroll/scroll-props.ts
@@ -7,8 +7,8 @@
 export type ScrollCallback = (scrollState: ScrollState) => void
 
 export interface ScrollProps {
-  scrollState?: ScrollState
-  onScroll?: ScrollCallback
+  scrollState?: ScrollState | null
+  onScroll?: ScrollCallback | null
   onMakeScrollSource?: () => void
 }
 
diff --git a/frontend/src/components/global-dialogs/motd-modal/motd-modal.tsx b/frontend/src/components/global-dialogs/motd-modal/motd-modal.tsx
index 872b9bfb5..d732f8634 100644
--- a/frontend/src/components/global-dialogs/motd-modal/motd-modal.tsx
+++ b/frontend/src/components/global-dialogs/motd-modal/motd-modal.tsx
@@ -30,7 +30,7 @@ export const MotdModal: React.FC = () => {
   const { error, loading, value } = useAsync(fetchMotd)
   const [dismissed, setDismissed] = useState(false)
 
-  const lines = useMemo(() => value?.motdText.split('\n'), [value?.motdText])
+  const lines = useMemo(() => value?.motdText.split('\n') ?? [], [value?.motdText])
 
   const dismiss = useCallback(() => {
     if (value?.lastModified) {
@@ -51,7 +51,7 @@ export const MotdModal: React.FC = () => {
 
   return (
     <CommonModal
-      show={!!lines && !loading && !error && !dismissed}
+      show={lines.length > 0 && !loading && !error && !dismissed}
       titleI18nKey={'motd.title'}
       {...cypressId('motd-modal')}>
       <Modal.Body>
@@ -59,7 +59,7 @@ export const MotdModal: React.FC = () => {
           <RendererIframe
             frameClasses={'w-100'}
             rendererType={RendererType.SIMPLE}
-            markdownContentLines={lines as string[]}
+            markdownContentLines={lines}
             adaptFrameHeightToContent={true}
             showWaitSpinner={true}
           />
diff --git a/frontend/src/components/global-dialogs/settings-dialog/global/language-option.tsx b/frontend/src/components/global-dialogs/settings-dialog/global/language-option.tsx
index a351726b2..ef30502a9 100644
--- a/frontend/src/components/global-dialogs/settings-dialog/global/language-option.tsx
+++ b/frontend/src/components/global-dialogs/settings-dialog/global/language-option.tsx
@@ -17,7 +17,7 @@ interface LanguageOptionProps {
  */
 export const LanguageOption: React.FC<LanguageOptionProps> = ({ languageCode }) => {
   const displayName = useMemo(
-    () => new Intl.DisplayNames([languageCode], { type: 'language' }).of(languageCode),
+    () => new Intl.DisplayNames([languageCode], { type: 'language' }).of(languageCode) ?? null,
     [languageCode]
   )
 
diff --git a/frontend/src/components/markdown-renderer/markdown-to-react/markdown-to-react.tsx b/frontend/src/components/markdown-renderer/markdown-to-react/markdown-to-react.tsx
index 06a5ea88f..c34e4e3e9 100644
--- a/frontend/src/components/markdown-renderer/markdown-to-react/markdown-to-react.tsx
+++ b/frontend/src/components/markdown-renderer/markdown-to-react/markdown-to-react.tsx
@@ -41,12 +41,14 @@ export const MarkdownToReact: React.FC<MarkdownToReactProps> = ({
 
   useMemo(() => {
     nodeToReactTransformer.setReplacers(markdownRenderExtensions.flatMap((extension) => extension.buildReplacers()))
+    return null //todo: replace usememo hack
   }, [nodeToReactTransformer, markdownRenderExtensions])
 
   useMemo(() => {
     measurePerformance('markdown-to-react: update-line-mapping', () => {
       nodeToReactTransformer.setLineIds(lineNumberMapper.updateLineMapping(markdownContentLines))
     })
+    return null
   }, [nodeToReactTransformer, lineNumberMapper, markdownContentLines])
 
   const nodePreProcessor = useCombinedNodePreprocessor(markdownRenderExtensions)
diff --git a/frontend/src/components/register-page/register-error.tsx b/frontend/src/components/register-page/register-error.tsx
index ca52bced6..a053b10e7 100644
--- a/frontend/src/components/register-page/register-error.tsx
+++ b/frontend/src/components/register-page/register-error.tsx
@@ -17,7 +17,7 @@ export const RegisterError: React.FC<RegisterErrorProps> = ({ error }) => {
 
   const errorI18nKey = useMemo(() => {
     if (!error) {
-      return undefined
+      return null
     }
     return new ErrorToI18nKeyMapper(error, 'login.register.error')
       .withHttpCode(409, 'usernameExisting')
@@ -28,7 +28,7 @@ export const RegisterError: React.FC<RegisterErrorProps> = ({ error }) => {
 
   return (
     <Alert className='small' show={!!errorI18nKey} variant='danger'>
-      <Trans i18nKey={errorI18nKey} />
+      <Trans i18nKey={errorI18nKey ?? ''} />
     </Alert>
   )
 }
diff --git a/frontend/src/components/render-page/hooks/sync-scroll/use-document-sync-scrolling.ts b/frontend/src/components/render-page/hooks/sync-scroll/use-document-sync-scrolling.ts
index 2c23bcdbf..b6f61758d 100644
--- a/frontend/src/components/render-page/hooks/sync-scroll/use-document-sync-scrolling.ts
+++ b/frontend/src/components/render-page/hooks/sync-scroll/use-document-sync-scrolling.ts
@@ -26,10 +26,10 @@ export const useDocumentSyncScrolling = (
   outerContainerRef: React.RefObject<HTMLElement>,
   rendererRef: React.RefObject<HTMLElement>,
   numberOfLines: number,
-  scrollState?: ScrollState,
-  onScroll?: (scrollState: ScrollState) => void
+  scrollState: ScrollState | null,
+  onScroll: null | ((scrollState: ScrollState) => void)
 ): [(lineMarkers: LineMarkerPosition[]) => void, React.UIEventHandler<HTMLElement>] => {
-  const [lineMarks, setLineMarks] = useState<LineMarkerPosition[]>()
+  const [lineMarks, setLineMarks] = useState<LineMarkerPosition[]>([])
 
   const recalculateLineMarkerPositions = useCallback(
     (linkMarkerPositions: LineMarkerPosition[]) => {
diff --git a/frontend/src/components/render-page/hooks/sync-scroll/use-on-user-scroll.ts b/frontend/src/components/render-page/hooks/sync-scroll/use-on-user-scroll.ts
index d22550e9d..1cb40d20b 100644
--- a/frontend/src/components/render-page/hooks/sync-scroll/use-on-user-scroll.ts
+++ b/frontend/src/components/render-page/hooks/sync-scroll/use-on-user-scroll.ts
@@ -19,7 +19,7 @@ import { useCallback } from 'react'
 export const useOnUserScroll = (
   lineMarks: LineMarkerPosition[] | undefined,
   scrollContainer: React.RefObject<HTMLElement>,
-  onScroll: ((newScrollState: ScrollState) => void) | undefined
+  onScroll: ((newScrollState: ScrollState) => void) | null
 ): React.UIEventHandler<HTMLElement> => {
   return useCallback(() => {
     if (!scrollContainer.current || !lineMarks || lineMarks.length === 0 || !onScroll) {
diff --git a/frontend/src/components/render-page/hooks/sync-scroll/use-scroll-to-line-mark.ts b/frontend/src/components/render-page/hooks/sync-scroll/use-scroll-to-line-mark.ts
index 60782489f..d9e6bf38f 100644
--- a/frontend/src/components/render-page/hooks/sync-scroll/use-scroll-to-line-mark.ts
+++ b/frontend/src/components/render-page/hooks/sync-scroll/use-scroll-to-line-mark.ts
@@ -18,8 +18,8 @@ import { useCallback, useEffect, useRef } from 'react'
  * @param scrollContainer The container to scroll in
  */
 export const useScrollToLineMark = (
-  scrollState: ScrollState | undefined,
-  lineMarks: LineMarkerPosition[] | undefined,
+  scrollState: ScrollState | null,
+  lineMarks: LineMarkerPosition[],
   contentLineCount: number,
   scrollContainer: RefObject<HTMLElement>
 ): void => {
diff --git a/frontend/src/components/render-page/renderers/document/document-markdown-renderer.tsx b/frontend/src/components/render-page/renderers/document/document-markdown-renderer.tsx
index e785eb40d..6f30e8f2d 100644
--- a/frontend/src/components/render-page/renderers/document/document-markdown-renderer.tsx
+++ b/frontend/src/components/render-page/renderers/document/document-markdown-renderer.tsx
@@ -57,8 +57,8 @@ export const DocumentMarkdownRenderer: React.FC<DocumentMarkdownRendererProps> =
     internalDocumentRenderPaneRef,
     rendererRef,
     contentLineCount,
-    scrollState,
-    onScroll
+    scrollState ?? null,
+    onScroll ?? null
   )
 
   const markdownBodyRef = useRef<HTMLDivElement>(null)
diff --git a/frontend/src/components/render-page/window-post-message-communicator/hooks/use-editor-receive-handler.ts b/frontend/src/components/render-page/window-post-message-communicator/hooks/use-editor-receive-handler.ts
index 61d5bbcb8..3dfa75267 100644
--- a/frontend/src/components/render-page/window-post-message-communicator/hooks/use-editor-receive-handler.ts
+++ b/frontend/src/components/render-page/window-post-message-communicator/hooks/use-editor-receive-handler.ts
@@ -16,7 +16,7 @@ import { useEffect } from 'react'
  */
 export const useEditorReceiveHandler = <R extends RendererToEditorMessageType>(
   messageType: R,
-  handler?: Handler<CommunicationMessages, R>
+  handler: Handler<CommunicationMessages, R> | null
 ): void => {
   const editorToRendererCommunicator = useEditorToRendererCommunicator()
   useEffect(() => {
diff --git a/frontend/src/components/render-page/window-post-message-communicator/hooks/use-send-to-renderer.ts b/frontend/src/components/render-page/window-post-message-communicator/hooks/use-send-to-renderer.ts
index e87cf1cf4..f6665d9f6 100644
--- a/frontend/src/components/render-page/window-post-message-communicator/hooks/use-send-to-renderer.ts
+++ b/frontend/src/components/render-page/window-post-message-communicator/hooks/use-send-to-renderer.ts
@@ -15,7 +15,7 @@ import { useEffect } from 'react'
  * @param rendererReady Defines if the target renderer is ready
  */
 export const useSendToRenderer = (
-  message: undefined | Extract<CommunicationMessages, MessagePayload<EditorToRendererMessageType>>,
+  message: null | Extract<CommunicationMessages, MessagePayload<EditorToRendererMessageType>>,
   rendererReady: boolean
 ): void => {
   const iframeCommunicator = useEditorToRendererCommunicator()
diff --git a/frontend/src/components/slide-show-page/slide-show-page-content.tsx b/frontend/src/components/slide-show-page/slide-show-page-content.tsx
index a329da6d2..050f69012 100644
--- a/frontend/src/components/slide-show-page/slide-show-page-content.tsx
+++ b/frontend/src/components/slide-show-page/slide-show-page-content.tsx
@@ -27,7 +27,7 @@ export const SlideShowPageContent: React.FC = () => {
   useSendToRenderer(
     useMemo(() => {
       return !slideOptions
-        ? undefined
+        ? null
         : {
             type: CommunicationMessageType.SET_SLIDE_OPTIONS,
             slideOptions
diff --git a/frontend/src/extensions/essential-app-extensions/csv/csv-table.tsx b/frontend/src/extensions/essential-app-extensions/csv/csv-table.tsx
index d2001901f..a3c26f745 100644
--- a/frontend/src/extensions/essential-app-extensions/csv/csv-table.tsx
+++ b/frontend/src/extensions/essential-app-extensions/csv/csv-table.tsx
@@ -38,7 +38,7 @@ export const CsvTable: React.FC<CsvTableProps> = ({
   }, [code, delimiter, showHeader])
 
   const renderTableHeader = useMemo(() => {
-    return headerRow.length === 0 ? undefined : (
+    return headerRow.length === 0 ? null : (
       <thead>
         <tr>
           {headerRow.map((column, columnNumber) => (
diff --git a/frontend/src/hooks/common/use-single-string-url-parameter.ts b/frontend/src/hooks/common/use-single-string-url-parameter.ts
index c0aeb6960..ac0eda112 100644
--- a/frontend/src/hooks/common/use-single-string-url-parameter.ts
+++ b/frontend/src/hooks/common/use-single-string-url-parameter.ts
@@ -16,7 +16,6 @@ import { useMemo } from 'react'
 export const useSingleStringUrlParameter = <T>(parameter: string, fallback: T): string | T => {
   const router = useSearchParams()
 
-  return useMemo(() => {
-    return router?.get(parameter) ?? fallback
-  }, [fallback, parameter, router])
+  const value = useMemo(() => router?.get(parameter) ?? null, [parameter, router])
+  return value ?? fallback
 }
diff --git a/frontend/src/hooks/common/use-trimmed-note-markdown-content-without-frontmatter.ts b/frontend/src/hooks/common/use-trimmed-note-markdown-content-without-frontmatter.ts
index 9fee3ba39..afe2c824d 100644
--- a/frontend/src/hooks/common/use-trimmed-note-markdown-content-without-frontmatter.ts
+++ b/frontend/src/hooks/common/use-trimmed-note-markdown-content-without-frontmatter.ts
@@ -29,7 +29,7 @@ export const useTrimmedNoteMarkdownContentWithoutFrontmatter = (): string[] => {
 
   const trimmedLines = useMemo(() => {
     if (!markdownContent) {
-      return undefined
+      return null
     }
     if (markdownContent.content.length > maxLength) {
       return markdownContent.content.slice(0, maxLength).split('\n')
@@ -39,6 +39,6 @@ export const useTrimmedNoteMarkdownContentWithoutFrontmatter = (): string[] => {
   }, [markdownContent, maxLength])
 
   return useMemo(() => {
-    return trimmedLines === undefined || lineOffset === undefined ? [] : trimmedLines.slice(lineOffset)
+    return trimmedLines === null || lineOffset === undefined ? [] : trimmedLines.slice(lineOffset)
   }, [lineOffset, trimmedLines])
 }