There are tons of dumb TVs out there but they're more expensive because the ads and data harvesting subsidizes the cost.
I know it's not a perfect suggestion but I agree with the other comment: buy a smart TV and never connect it to the internet. The vast majority of displays don't gain anything (outside of the "smart" features) with firmware updates. The exceptions to that are very rare.
It sucks to have to buy a streaming box on top of it but the two items combined is less than a commercial (dumb) display. Even at cost.
Though instead of a Chromecast for streaming, I'd consider an AppleTV...I'm not a fan of Apple but it's hands down the best streaming box I've used outside of a dedicated HTPC.