Recommendations to purchase a smart TV but never connect it to a network are futile, as well. Just like Amazon devices, smart TVs will find an open SSID and then phone home for updates without your knowledge.
My recommendation, when these kind of topics come up, is: either exchange your smart TV for a dumb one, or go to an electronics repair shop to have a board or two exchanged (depending on the make and model, older dumb components may be direct-ish replacements for smart ones).
EDIT: Another option? Try a projector! I was looking for dumb TV options online after writing up this comment, and someone on an old Reddit post recommended it. Great idea.