Find one you like and just don't connect it to the network?

Most TV's won't freak out if they lack an internet connection and are still fully functional (outside of services that require internet), and many can be updated via firmware on USB thumbdrive over sneakernet.

This is also more futurepoof - I have a relatively ancient (in TV timelines) Vizio that is so old that none of the apps were working with modern services (and even when they worked the were slow/laggy), so I just unplugged ethernet and drove it from other HDMI sources.

Most TV's won't freak out if they lack an internet connection...

If only this was true.

Some (if not most) check for a connection on power up and "freak out" by launching into setup if there isn't one --- unless you run the TV in store/demo mode.

Backing out of setup on every startup is possible --- but it is often a multi-step process that becomes extremely annoying. Basically, they try to frustrate you into connecting --- unless you run the TV in store/demo mode.

I have a lower end Hisense 55" QLED model from Costco (roughly $250) that I run in this "dumb" store mode connected to my own "smarts" that I control.

Some models can find unprotected networks and connect automatically to them the same second someone accidentally opened such network and upload all accumulated data.