I’m experiencing the same issue with YouTube TV audio via AirPlay to my HomePod (in some cases there’s no audio at all). I reached out to YouTube TV support, and they were completely unhelpful. They suggested I reach out to Apple stating:
“Thanks for your response and clarification. You mentioned that the audio is syncing correctly if you use the speakers for your TV at this point the YouTube TV app is working as intended.It looks like that the the HomePod has a delay on picking up the Audio from your Apple TV to your HomePod.
At this case, I would suggest to contact Apple support for your HomePod so they can provide steps on how to improve the syncing of Audio for your devices. You can contact the Apple support by phone at
1-800-275-2273 or through their online support options:
getsupport.apple.com.“
My issue began Thursday evening, or that’s when I first saw it. I know it worked Thursday morning.