In the lot of iOS 12.1 beta 1 and watchOS 5.1 beta 1, Apple offers us tvOS 12.1 beta 1 for download for Apple TV shortly after the final version of tvOS 12 (cf. The final version of tvOS 12 is available for download) .
The new features that were introduced with this new pre-version (build 16J5575c) are not known at the time these lines are written due to the lack of changelog available. It will therefore be necessary to wait for the first feedback from the developers to find out more.
To install tvOS 12 beta 1 on your Apple TV, if you have a developer profile, go to the settings, in the section dedicated to updates and follow the displayed steps.
Other recent betas: