Apple has released tvOS 12.0.1 for Apple TV 4 and Apple TV 4K on Monday. The release notes are essentially mother about new features, and this release is probably a minor bug fix release or related to macOS Mojave, which was also released on Monday.
Apple TV 4K
tvOS 12 appeared a week ago on 17 September. It added new screensavers that were recorded on the International Space Station, support for Dolby Atmos and Zero Sign-on for cable TV services.
tvOS 12.0.1 can be downloaded via Apple TV 4 and Apple TV 4K Settings gt; System gt; Software update.