still no support for airplay streaming to a homepod stereo pair from system audio (e.g. spotify or youtube) in macOS. you can stream to one or the other, but not both. (ios and ipados and tvos and even itunes.app on macos can all stream to a homepod stereo pair.)
when will this nonsense end
here i am sitting in a room with $700 of wireless speakers and listening to a song out of my laptop speakers. cool move, apple