Designed for the fourth and fifth-generation Apple TV models, the tvOS 11.1 beta can be downloaded onto the Apple TV via a profile that's installed using Xcode on the Mac.
The tvOS 11.1 update appears to focus on bug fixes and performance improvements rather than outward-facing design changes, and no new features were found in the first two betas. Should anything notable surface in the third tvOS 11.1 beta, we'll update this post.
tvOS 11 introduces features like full support for AirPods, automatic switching between light and dark mode based on local time, Home screen syncing options designed to keep multiple Apple TVs in a single household in sync, and new background modes and notification support.
Update: Apple has also released a new tvOS 11.1 beta for public beta testers.