Did you ever have to pass Appstore review process? How do they look at copyright and stuff when you are publishing an app that plays your local mp3 collection (how does your mp3 collections ends up on your phone?)
For now I'm letting that backend access my files directly. The front end can also play YouTube music (free, using the yt-dlp method).
None of this is public yet so right now I don't need anyone's approval.