Last week, Apple released tvOS 15.1, which introduced several notable new features, including SharePlay, HomePod compatibility updates, and more. Today's tvOS 15.1.1 release brings further refinements and improvements to those features.
The build number for today's update is 19J581, but Apple has not provided any release notes at this time detailing the innovations or changes. The update is probably focused on fixing minor bugs and performance improvements.
You can update your Apple TV 4 and Apple TV 4K set-top boxes to tvOS 15.1.1 by going to the Settings app, selecting System and then Software Update.