The best privacy method is to completely disconnect the TV from any wired or wireless network, and like you suggested to use it as a dummy display with the Apple TV (or whichever your favorite media player is). So in that sense you could just go to Costco (or any major electronics retailer if not in US) and pick one that you like the image & price.
I guess I am more concerned about random devices at home that need internet to work yet I have no idea what data they send where.
Not sure about the US experience, but here in Australia there are no dumb TVs for sale in our retail electronics stores. Every TV comes with some sort of "smart" OS.
It's the same way in the US. That's why they were saying to just buy any TV (which will almost certainly be a smart TV), then just treat it like a dumb TV by not connecting it to the internet.
I was able to disable a bunch of stuff on my LG so I never actually see the WebOS interface anymore.
I would disconnect the WiFi antenna as well and hope it doesn’t connect to nearby WebOS TVs via Bluetooth to pass telemetry so that the other TV uploads it to their mothership.
I assume that, in Europe, they’d need to be GDPR compliant, so that is a layer of protection the manufacturer can’t skip.