Theoretically if you never hook a smart TV to the net it shouldn’t be able to spy.

I think you are right (today!), but look what happens with cars... the car connects to a wireless network without asking you, to send back telemetry. The cost of doing that is coming down all the time, and there is a big juicy profit stream just waiting to be harvested. I will not be surprised if we see TVs do this eventually, like cars do already.

They could also be designed to simply refuse to function if they can't connect. I didn't hear about any like this so far, but it feels like a matter of time. Enshittification comes for everything.