“Well, for starters, don’t buy smart TVs in the first place. Apple TV and Roku, to name two, supply pretty much everything a smart TV does and more. Sure, they can have security holes as well, but at least they’re designed by people with a clue about security and network engineering.
What’s that? You already have a smart TV? Bite the bullet, disconnect it from the internet, and turn it into a dumb TV.
First, check to see if your TV will let you disconnect from your Wi-Fi network. If it won’t, reset it to its factory default setting. When it turns on again and goes through its setup routine, don’t give it your Wi-Fi password.
If you’re using Ethernet, do the same thing — except this time, you simply don’t plug it into your network.”