I use mpd-sima for autoplay functionality. It would in turn require using mpd or mopidy.
It queries last.fm for recommended artists and tries to find a match in your playlist. It works, but honestly it’s not great. I don’t think it’s any fault of the software. Last.FM doesn’t know your library and seems to return limited results, so it’s like a game of battleship actually getting a hit. (Not quite that bad, but the analogy holds water, overall)