https://wccftech.com/how-to-clean-install-tvos-14-final-version-on-apple-tv-hd/

Apple has released tvOS 14 to all users today with a bunch of new features and upgrades. If you have an Apple TV HD, you have the option available to perform a clean install tvOS 14.

As mentioned earlier, Apple has released tvOS 14 for all compatible Apple TV models. This includes the Apple TV HD and the Apple TV 4K. On the Apple TV HD, you have the option and luxury to perform a clean install of tvOS 14. Take note that you cannot perform a clean install on the Apple TV 4K. This is due to the fact that the Apple TV 4K does not house a USB-C port. So clean installing tvOS 14 is only available for the Apple TV HD. Before we go ahead with the tutorial, you will need a USB-C cable to go through the process.