Further to these issues, I've found albums which have cover art in my pre Catalina library and that art is lost in Catalina. Typically when I use the technique of playing some songs the art is indexed and shows up, however in some situations that doesn't work. In addition to that I ask Music to get album artwork and it fails.
So in summary, not only have I lost the artwork for this album in the transition from iTunes to Music. It isn't an automatic exercise to recover the artwork, so now I am going to be asked to revisit a large portion of my approximately 3,313 albums to then search for artwork in a web browser, (something I had already done at least once).
I suspect there is a larger underlying bug or omission in development of the transition of libraries from iTunes to Music. Let's hope that Apple considers this issue and has not completely moved on to only developing for Music subscribers.