Here's some tools i used and my experience with them
- beets: very powerful CLI tool. Has a learning curve but can go through your whole music folder, automatically tag stuff it is confident in and prompt you when it's not sure.
- musicbrainz picard: really powerful gui. Can add a bunch of folders, group them by album and have it detect the right albums.
- kde kid3: simple gui app that if all you're looking for is basic tag input then it makes it super easy to manually tag a bunch of content all at the same time.
I personally used all three of these. Beets as first pass that got me pretty far. Music brainz to fill in a lot of holes. And kid3 when i just wanted to do a bunch of manual updates
For iTunes based music player there is also rhythmbox which is standalone (no subsonic server needed). It's what i used until i ultimately switched to navidrome + supersonic. I'll check out feishin since that didn't come up in my initial search last year. Ive liked supersonic though. It has a decent, simple UI and you can play albums by clicking on them
Edit: ok feishin seems pretty cool. I might stick with this