If you leave the smart-TV without a network connection it'll be mostly like a plain TV.

> try buying non-smart phone

There are some feature phone Nokia models available, I use one such.

The thing I miss the most about having a smartphone is GPS and a map app. For everything else except mobile internet, which I can do without, that a smartphone would give me I have an iPod touch.

Disable data connection for both and you have "dumb" counterparts. Of course, you still pay for unnecessary features, but it's the price to pay if you value your privacy.

Unless you've physically removed or disconnected the wireless interface, there's still a chance that a firmware vulnerability could lead to your TV being hacked via a remote and/or side-channel attack similar to what was demonstrated in the article.