It’s not for Sonos to fix. Each service is responsible for their own implementation and content within the Sonos app. All Sonos does is maintain the API, the service does all the work. So this is a question for YouTube, not Sonos.
ok i imagine as Youtube music increases in popularity they will work to resolve this. Its obviously an ongoing issue from the number of past posts. Sad to see it lingering this long as an issue.
The solution I found in the interim is to turn on my Samsung TV, navigate to the YouTube app - where i DO see my playlists - and run the music off there, obvi playing through my Arc. Definitely inconvenient, but effective.
Actually several of the YTM threads recently reported the audio-dropout problem seems to have been fixed, so there are slight signs of progress from Google.