Apple has seeded tvOS 15.3 and HomePod software 15.3 to the public, with the new updates focusing mainly on platform stability, bug fixes, and ecosystem improvements.
The tvOS update will be installed automatically, but it can be manually installed onto an Apple TV via the Settings app as well. Users can update their HomePods from the Home app on iOS or macOS.
Updates to tvOS are generally incremental maintenance releases, adding support for products and services while also improving the experience in small ways. Occasionally, the updates introduce new features, but at this early stage, it doesn't seem to be the case for this release.
In December, Apple Released tvOS 15.1, which added support for Apple Music Voice, Apple's new budget Apple Music plan.
The build number for tvOS 15.3 and HomePod software 15.3 is 19K547, up from 19K545 in the release candidate.
In October, Apple released tvOS 15.1 which introduced SharePlay to the public, and added a handful of new screensavers. SharePlay, which Apple announced during WWDC 2021, allows users to watch video content with others while on a FaceTime call.