In Tahoe, Apple Music not playing mp3s from library

I just upgraded my iMac to Tahoe (from Big Sur). I'm a long-time iTunes user and have a largish library of (legally) downloaded mp3s (including a lot of niche stuff that's not easily available for streaming). Prior to this upgrade, all my carefully organized music played fine in Apple Music. But now it doesn't. When I click play on an album, on the control bar at the bottom it looks like the app very rapidly (in a split second) cycles through all of the album songs, but doesn't play any. Needless to say, suddenly not having access to any music is extremely frustrating.

Here's what I did so far to try to fix the issue:

• Restarted everything (duh)
• Reset the music store cache in Settings
• Authorized the computer/ signed in to Apple Music
• Looked for a library cache to delete, but couldn't find it where the internet told me it would be
• Checked the file path of my music. Everything is where it's supposed to be and the app is pointing at the correct folders.

Note that I do not have a paid Apple Music subscription and I'm not interested in getting one; I just want to use the app as a good old-fashioned mp3 player.

I'm kind of at a loss here. Is this a bug that will be fixed? Am I screwed? Is there any way I can revert to a previous version of Apple Music (without reinstalling the OS)? Should I give up and just use another player that will play all my files (and hopefully recognize all of the metadata) and if so which one is best? Any help would be appreciated!