Homekit in a television is more of a device, like a light bulb or door lock
Think of HomeKit on a TV as basically a fancy remote control.
it allows you to turn the TV on and off, and select inputs,
You can also use the remote widget from control panel on your phone as a basic remote (volume, direction arrows, enter, and back)
---It also means the TV probably supports airplay, and possibly has the Apple store built in, But those features vary.
a HomeKit hub allows you to control your devices from outside your home.
The AppleTV is a hub.
On the appleTV, there is no Home app.
The only setting is on the iCloud sign-in page, and it's a simple yes/no to be a hub or not.
the only way to interact with HomeKit on the appleTV is controlling other devices through Siri on the remote (there are a couple of third party apps, but in my experience, they're pretty useless)
a Homekit hub can be any of these devices... homepod, appleTV, or iPads
as of now, I don't think a third party TV can be a hub.
Homekit doesn't need a hub to work, your phone just has to be on the same network if you don't have one.
Homekit is a language that apple has designed for different devices to be controlled and to report their status back.
it allows a lightbulb to say "I'm a lightbulb, I turn on and off, and support dimming to levels in between"
the phone then knows how to interpret that, and can say "Hey lightbulb, turn on to 50%"
the bulb will the say back "OK, I'm at 50%"
With HomeKit you can make scenes, which you can put your tv into.
so a scene called "watch TV" could ... "turn on the TV, put it to HDMI 1, and dim all the lights in your living room to a low level"
you can also make automatons that happen when things turn on or off,
you could make an automation that if the TV turns on (even if you hit the power button on the TV itself), it automatically turns off all the lights and locks the front door (if you have the appropriate HomeKit devices)
