Unfortunately that is a legitimately missing piece for the wide community atm. I’ve filled the gap myself with a personal app that pulls recommendations from deezer/musicbrainz. As I rate things up in it, it starts displaying new recommendations to me based on those bands. I might polish it up and release down the road if I get some spare cycles

iTunes had smart playlists? Ahead of its time!

Not true. I self host my music, which is what got me into homelabbing in the first place. I have 7 months+ playtime of music, and a pipeline for finding new recommended content with it. And i get the benefit of not having my music removed when license deals expire or never existed. And my random play actually randomizes instead of whatever profit optimized engine Spotify pretends to be “random” playing, so I actually hear new stuff. And I have playlists that can have more than 10k songs, but I dont even need those because I have smart playlists, including ones set up to only play things i havent ever listened to. I wouldnt ever go back