Apple today released tvOS 11.1 for the fourth-generation Apple TV and the new Apple TV 4K.
To update your device to the latest available version of tvOS, go to Settings → System → Software Updates → Update Software and follow the onscreen instructions.
The tvOS 11.1 software update focuses mostly on under-the-hood changes and bug fixes, with very little outward-facing changes or new features. Apple yesterday began testing the upcoming tvOS 11.2 software update with its developers.
tvOS 11.2 provides new options in Settings for auto-switching of the system video mode to match the native frame rate and dynamic range of video content being played rather than upscale everything to the current video output mode.