I have two HomePods playing as a stereo pair connected to one of my AppleTVs. It used to be that every time I started my AppleTV and wanted to play the auto of whatever I was watching, I would have to go to the output option on AppleTV and direct the audio to the HomePods. Now it works as it should for most apps including iTunes movies, Netflix, etc. but not YouTube. I just start the AppleTV, select a movie from iTunes or Netflix, and the sound comes out through the HomePods! Yeah! This doesn't work in YouTube yet but there is hope.