I simply bought a non-smart TV. I just made sure it had a number of HDMI ports. I plug my various media sources into the HDMI ports.
A "smart" TV must be the most un-smart TV possible - you're stuck with whatever's there. The "smart" part (say, a Pi or a Chromecast or both) must be detached from the display device (the TV), not a part of it.
"smart" TVs remind me of back when I bought a webcam with integrated Skype, for my old parents. It did make it easy for them to skype with their grandchildren, using the TV. But of course Skype, or MS at the time, plugged the pull on the version of Skype used by the webcam and then it became a brick. Never again.
