Today, Apple has released a new operating system update for the Apple TV HD and Apple TV 4K. tvOS 15.6 addresses some performance and stability improvements. tvOS 15.6 is compatible with the Apple TV HD and Apple TV 4K and can be downloaded now.
To update your Apple TV go to Settings > System > Software Update. Most Apple TVs have automatic software updates enabled, so the update should happen on its own.
Apple’s release notes say tvOS 15.6 includes “general performance and stability improvements.” However, the release notes for tvOS are generally sparse, so there might be more to it.