From Apple Support:

With HDMI ARC or eARC turned on, your Apple TV 4K (2nd generation) can receive high-quality audio from a supported TV and then play that audio through your HomePod speakers.

ARC support is what made me decide to buy a new Apple TV 4K despite buying one just last year. I am happy to report that it works well, even on my five-year-old Vizio. Now my Switch, my Playstation 4, and even broadcast TV also sound great on my HomePods. The whole experience serves as even more evidence that the HomePods should have been marketed as a home theater product from the beginning, where sound quality matters as much, if not more, than price.