There really isn't anything because there isn't much reason to do it beyond "because I can".

The SoCs used in smart TVs are mostly older ARM and MIPS chips with just enough power for what they need to do so it's not like a game console where it's an interesting development target.

Beyond that, by their nature TVs have inputs, so plugging in your own device that runs whatever you want is trivial, so there's no real need to get something running on that device specifically when you can shove a stick in a HDMI socket and make it do whatever.

If the telemetry and whatever are your main concern you can just not connect the TV to the internet in the first place.