Apple TV 4k

It should register as home hub automatically, when configured with the same Apple ID account for iCloud services.

Set up your HomePod, HomePod mini, Apple TV, or iPad as a home hub - Apple Support

Management of HomeKit functionality is done through the Home app on iPhone or iPad however, not on Apple TV.

Unfortunately, AppleTV doesn't really play a part in HomeKit, outside of you being able to view it in the Home App on your other devices.

You cannot control much from AppleTV.