For my offline music library I manually edit the tag/info/metadata from Oto or Musicolet.
Then I use Oto Music Player to download synced lyrics coz it can automatically download the synced lyric with one press of a button.
Then I use Musicolet to download album art. I manually download HD image for album art from google (usually from Apple music).
Now I have 1000+ meticulously organized FLAC files, outside that I still have many music files that not tagged properly.
Edit: All that files already organized by artist/album artist per folder. Then I manually transfer all that edited file to my external drive for backup.
I mainly use Retro Music player from my Android phone coz it’s simple and pleasant UI. (Tho I hope Retro can have all that Oto and Musicolet feature I mention, plus Hiby/UAPP bit perfect feature).
L’imperatrice- Odyssey