There are many threads regarding the way how Plex handles genres, one of them is
“Genres are track specific, not album specific, so why does Plex do this?”
I have the same problem like desrcibed in this thread from 2021, but obviously the issue has not been resolved.
I have re-configured my music library to read the genres from the embedded tags, and re-scanned the library files, but I still do not find the track genres I use, but many genres I never use.
Do I really have to re-create the library with the embedded tags setting? Due to the fact that I have over 400.000 files I would be reluctant to do that.
Btw, ‘Artist genre’ is another metadata which is pretty useless imho.