Big Sur 11.2 will likely be released in the next week or two. I’m not optimistic that they’ve fixed this (I don’t see any mention of it in beta forums), but we can hope.

The Big Sur 11.3 update did finally fix this issue. You can once again use AppleScript to get the album artwork of the current track even if the track hasn’t been added to your music library.

@blue_lander I noticed that too. Even though song title, artist, and cover art now work, I still can’t get the album name for any track that has not been added to my library.