Am I missing something? I have a LG nano something TV that has many “smart” features, but I never let it connect to my WiFi ever. Since day 1 it has been hooked up to an AppleTV. Can I not buy any fancy smart TV in 2025 and use it as a dumb HDMI display for AppleTV?

Same. I have not seen the interface of my TV for years (Only the input switching UI when switching between my Apple TV and Xbox). This really isp pretty much a "dumb tv" with a setup like this.

the issue is that eventually SIM cards will be baked in to deliver ads and spyware; there will be no alternatives because everyone was fine with buying smart TVs and not connecting them to wifi.

see: Android's recent transformation into a closed platform which no longer allows users to control devices they purchase. it's important to fight against trends like this loudly and vehemently while we still can.

Second that. There were articles a year or two ago about TVs trying to connect to any open Wi-Fi they can find, without you asking them. But hopefully LG wouldn’t go that far.