It did not change anything for me. All problems remain. (I have my library on an external disk because it is too large to fit on the computer's disk.)
All tracks have album art embedded, but they show up only if I go to a track, cut the artwork, then paste it back in. Moreover, if I plug my external hard drive into a different Mac (also running 10.15.3), all artwork is now lost again. Moreover, all settings (e.g., playlist viewed as songs and sorted by year) reverts to default. Similarly, AMPLibrar still runs after quitting Music so external drive cannot be ejected without either force quit or finding the process id of AMPLibrar and killing it.
One issue seems to be that Music stores information not where your library actually is (i.e., the external drive) but in /Users/yourname/Library. This means when you plug the hard drive into a different computer (also running 10.15.3), you lose everything such as (1) the artwork you manually restored, (2) a playlist you sorted by year now reverts to sorted by album, etc. etc. and so on and so forth.