Reset Apple TV

You cannot. You can remove the Profile to stop receiving Beta updates, but you won't be able to go back to tvOS 13. You will only be able to update to the non-beta, final release of tvOS 14 when its released.

See here: https://beta.apple.com/sp/betaprogram/unenroll#tvos

Thanks for the additional information. For the 4K model, you will have to unenroll out of beta and wait for the final version, as Phil noted above. Only Apple technicians are able to restore this model externally.

What is your model Apple TV? Identify your Apple TV model - Apple Support

There are options for the one that aren’t available on the other (because of the USB service port).