I'm gonna go out on a limb and say that the hardware inside Smart TVs is far too piecemeal and random for anyone to be able to develop for more than one type of television set.

I mean, just look at the troubles AOSP offshoots like LineageOS have. They support a large number of devices, but that large number is literally just a drop in the fucking bucket of how many phones actually exist out there.

Each one of those phones has different hardware and needs different hardware drivers, which is why each phone generally has a different set of maintainers. The same would be an issue with these Smart TVs.

It's something that is feasible but feels like a waste of resources when you can just not connect your Smart TV to the internet and use a Roku/FireStick/Raspberry Pi running Kodi or go out of your way to purchase one of those commercial monitors that don't have any Smart TV bullshit in them.