Apple has discontinued the large HomePod recently, but the company is still adding useful features to it, such as lossless audio coming soon, spatial audio for Apple Music. And now it is going to become a much better device in a home theatre environment.
With the new Apple TV, support for HDMI ARC and eARC has been added, which would allow the Apple TV to send any audio received from the TV, from any other source straight to the HomePod. Essentially turning the HomePod + Apple TV 4K setup into a solid home theatre setup.
This setup only works with the new sixth generation Apple TV 4K and the discontinued HomePod. A TV compatible with (Audio Return Channel) and eARC (enhanced ARC) is also required, some TV manufacturers also call it something else, Panasonic for example call it Viera Link.
It also needs activating within tvOS, under Settings, the the Audio Output the option to select Audio Return Channel is in there.