If you want to extract audio from a video, you don't need external apps. You can use the Apple Shortcuts app and create an action to do it. I have searched this a dozen times, so here is how to do it:

1. Open Shortcuts App: Tap the + icon to create a new shortcut.
2. Name It: Tap the shortcut name (e.g., "Shortcut 1") and rename it (for example "Extract Audio").
3. Share Sheet Settings: Tap the 'i' icon at the bottom, enable "Show in Share Sheet," then tap "Done".
4. Receive Media: Tap the blue text under "Receive," clear all selections, and check only "Media," then tap "Done".
5. Add "Encode Media": Search for and add the "Encode Media" action.
6. Set to Audio Only: Tap the arrow next to "Encode Media," expand the options, and ensure "Audio Only" is toggled on (M4A is the default format).
7. Add "Save File": Search for and add the "Save File" action.
8. Ask Where to Save: Tap the arrow next to "Save File," and enable "Ask Where to Save".
9. Finish: Tap "Done" to save the shortcu