Homepod has problem with Apple Music -solved

I just bought a new Homepod 2 and Apple TV 4K 3rd generation (replacing older versions). Set up was fine and everything works except when I tried to ask Siri to play music from my Apple Music Library. There was a pause and Siri said she had a problem with Apple Music. Looking in this community and around the web, this is not an uncommon problem. I tried the recommended fixes (rebooting, switching router on and off, signing out of and back in to Apple Music etc, resetting Homepod), but nothing worked. I could play music through the Homepod by handing off from my iphone, but not via Siri and my music library.

Finally, I got a clue from a comment about using the Homepod as the default audio output for the Apple TV. I switched the Apple TV audio back to the TV speakers. Bingo! The Homepod/Apple Music problem was solved.

Hopefully this is helpful to others experiencing this problem. How come Apple can't get the integration across devices right yet?!