Well, one thing I suspected that I can now say is a problem with the new "Music" app...there were some songs that it refused to transfer to my iPod Classic. I posted the back story in another thread, but to sum it up, in the same session, I used XLD to rip the Beatles' new Abbey Road box set in Apple Lossless, and Chicago's Chicago Transit Authority (50th anniversary remix), also to Apple Lossless. Well...Apple Music had no problem transferring the Beatles stuff to my iPod, but it wouldn't let me transfer Chicago. If I dragged the songs over to the iPod in the sidebar, the little red box disappeared. (It would still let me transfer to my phone.) If I right-clicked on the songs and chose "Add to Device," the iPod wasn't an option. Even after I used the Apple Music option to convert the files to MP3 format: even the resulting MP3s wouldn't transfer.
On another thread there's a script that allows you to install iTunes in Catalina. Well...I just did that, and guess what: iTunes properly transferred the Chicago album that Music refused to.
So...instead of one master app to transfer music and podcasts, Apple wants me to use separate apps: one that refuses to copy artwork over, and another that might not actually want to transfer all of my songs over. Sure. This is a wonderful idea.
EDIT: Okay, maybe Catalina was trying to tell me something about Chicago Transit Authority. I finally got a chance to listen to it. The 50th anniversary remix is effing TERRIBLE!! Ughhgh. So maybe I should give Apple a pass on this one.