25 September 2019 Update: With the official release of tvOS 13.0 yesterday, we can now only downgrade from tvOS 13 beta to 13.0.
It's tempting to try out the beta tvOS but it is painful to be (I've been there) stuck on a buggy OS with slow or glitchy apps with the next update as your only way out.
When your device is enrolled in the Apple Beta Software Program, you will automatically receive new versions of the public beta from tvOS Software Update. At any time, you may unenroll your device so that it no longer receives these updates.
The catch for Apple TV 4K owners: only when the next version of commercial software is released, then you can install it from tvOS Software Update.
- Go to Settings.
To stop receiving the tvOS public betas, go to Settings > System > Software Update > and turn off Get Public Beta Updates.
Wait for next tvOS release.
Once your setting has changed, your Apple TV will no longer receive tvOS public betas. When the next commercial version of tvOS is released, it will automatically install if you have Automatic Software Update turned on. Or, you can install it from Settings > System > Software Updates > Update Software.