It appears (??) that yt-dlp works with youtube music, if you're signed in to youtube music.
Of course, it strips metadata and downloads opus files by default, but I think I'm find with both of those things.
[edit, if you --emebed-metadata it does do that thing.]
It's probably a violation of goog's TOS and would totally be copyright infringement, if you weren't downloading, say, music from the american public domain.