Real world, it's a royal pain in the butt trying to get a not-smart TV. There's a couple of companies that sell them at consumer-accessible prices and they aren't as frequently on the kinds of deep discounts bigger brands go for. You might just have to steer your parents towards using an Apple TV (the only ads are for Apple's own services plus nice integration with iPhones if your parents happen to be iPhone users) then set it up to boot straight to the Apple TV so they never see the Smart TV OS, and of course never connect the Smart TV to the Internet so whatever data harvesting it does do is useless