Mwk YouTube Music now apparently requires you to sign in in order to stream. The very latest version of Rimusic (can be acquired from Accrescent) has the following release notes:
What's New
Implemented YouTube Music Login in miscellaneous settings.
It work like piped and discord login, it's mandatory to listen songs, navigation not require it.
First time start app, go to miscellaneus settings and connect to YTM, restart app, try to play a song.
If not play, disconnect and login again, restart app, btw may not work? Create ticket with issue.
Enjoy RiMusic.