When you launch Xcode and then open Devices and Simulators, and connect your Apple TV 4K, you have a new menu item in Settings named Developer. If you close Xcode, the item stays, but if you restart the Apple TV 4K, it's gone until the next time you open Xcode and pair it again.
Is there a way to leave it there permanently? I'm not a developer, but it's still useful to me because it has the playback HUD with lots of information about the codecs, streaming bitrate and so on, and since I'm an A/V nerd, that is quite useful to me.