Apple issues tvOS 15.6 to the public with under-the-hood improvements
Apple has released tvOS 15.6 and HomePod software version 15.6 to the public with bug fixes.

The public release of tvOS 15.6 features under-the-hood bug fixes and improvements. Apple has not provided any information on any public-facing features.
HomePod software version 15.6 adds Siri voice recognition for Mandarin Chinese, Cantonese, and Japanese. It also includes software and stability improvements.
As with all releases of tvOS 15, it is compatible with Apple TV HD, and both generations of Apple TV 4K.
With the quiet announcement of tvOS 16 at WWDC 2022, major software features are expected to arrive later this Fall.
Earlier on May 25, Apple released tvOS 15.5.1 as part of a strategy to fix HomePod issues. Since both the HomePod and Apple TV devices share a release and build number for the software, an update was released for the Apple TV as well despite offering no new public-facing features.
Read on AppleInsider

The public release of tvOS 15.6 features under-the-hood bug fixes and improvements. Apple has not provided any information on any public-facing features.
HomePod software version 15.6 adds Siri voice recognition for Mandarin Chinese, Cantonese, and Japanese. It also includes software and stability improvements.
As with all releases of tvOS 15, it is compatible with Apple TV HD, and both generations of Apple TV 4K.
With the quiet announcement of tvOS 16 at WWDC 2022, major software features are expected to arrive later this Fall.
Earlier on May 25, Apple released tvOS 15.5.1 as part of a strategy to fix HomePod issues. Since both the HomePod and Apple TV devices share a release and build number for the software, an update was released for the Apple TV as well despite offering no new public-facing features.
Read on AppleInsider
Comments
I have two pairs of old-school HomePods, each pair connected to a ATV 4K, and set to do stereo audio with Atmos where applicable. In the last few months, I have one or the other of the HomePods in each pair disconnecting, or playing audio uncontrolled by ATV remote, etc. It is a constant project restarting and resetting the HomePods and ATVs to get things in alignment again. None of them chime off the doorbell, either.