How to fix a damaged Apple Music library on macOS Sequoia 15.4.1?

I opened Apple Music (Apple M1 OS 15.4.1) as normal and received a message: The library “Music Library (Damaged)” does not appear to be a valid music library. Music has created a new music library and renamed the damaged library to “Music Library (Damaged) (Damaged)”

So essentially, I've lost (not the music itself) but the entire playlist hierarchy – my Music app is a completely empty, blank interface.

I followed some advice, opened Music holding down Option and was prompted to Choose Music Library, chose a previous [hopefully] undamaged one, and nothing happened.

I have a backed up version of the most recent Library (no idea if it is damaged) but how do I restore Music, playlists etc to where it was a day or two ago?

[Re-Titled by Moderator]