After researching a new TV (where it only needs an Apple TV, no so-called smart features for spying purposes) the three contenders were Samsung, LG and Sony Bravia (the higher end models). Samsung was the least trustworthy, having played games with firmware updates and adding telemetry, LG was medium trustworthy, and Sony seemed the least likely. It looks like that heuristic was correct. For the Bravia, I put it on wifi just once temporarily to upgrade the firmware when I bought it, and I'm leaving it disconnected.

It can't just magically connect to an openwifi and update its firmware to start telemetry. It would need a new firmware to even try that.

Folks, never update a TV firmware unless it's necessary.