[RajT88]

My LG could be configured to behave like this (and believe me, I am thinking about going that way).

I have a cheap FireTV which cannot be made to behave this way. If you disconnect it from the internet, it will still require you to interact with the (slow-ass clunky) OS in order to select a different input.

Your best case scenario with some of these smart TV's is the ones which run Android to replace the launcher. Possibly, this gets reset periodically, meaning you have to keep doing it.

Apparently there's a few Fire devices which can be flashed with LineageOS - I might try researching that and see if it is doable. A FireTV stick with LineageOS would be the best case scenario.