In conjunction with macOS Mojave Apple has also released a minor maintenance update for the Apple TV and Apple TV 4K, tvOS 12.0.1.
If an Apple TV isn't configured to download updates automatically, tvOS 12.0.1 can be forced by opening the Settings app, then selecting System, Software Updates, and finally "Update Software."
It's so far unknown what's new in the software. Accompanying notes are empty, implying that it at best provides minor bug and security fixes.
tvOS 12 was originally released earlier this month. The upgrade brought long-delayed Dolby Atmos surround sound, as well "zero sign-on," allowing some people authenticate a cable provider without typing in credentials.
The software also enabled third-party remotes, password AutoFill, and smaller enhancements like NASA screensavers.