Apple today released new tvOS 16.3.1 and HomePod 16.3.1 software updates, with the software coming two weeks after the tvOS 16.3 and HomePod 16.3 updates were released.
According to Apple's release notes for HomePod software 16.3.1, the update includes general performance and stability improvements. Notes for tvOS 16.3.1 are unavailable as of yet, but are probably similar to the HomePod notes.
The tvOS 16.3.1 update can be downloaded over the air through the Settings app on the Apple TV by going to System > Software Update. Apple TV owners who have automatic software updates turned on will be upgraded to tvOS 16.3.1 automatically.
HomePod software is installed automatically on the HomePod unless the feature is disabled, but the HomePod can also be manually updated in the Home app by following the instructions in our HomePod update how to.
Source: Macrumors