Back before Christmas, I picked up a Sharp 40" set that was very much a dumb TV, exactly how I wanted it. Any smarts (for now, a Raspberry Pi running OSMC) plug into the HDMI ports.
About the only thing I can ding it for is that some buttons on the remote aren't available for CEC, so I still have to use my RC6 remote and IR receiver on the Pi to control Kodi for all but the most basic functions.
Also, if you're looking for a 4K set, I'm not sure there are any out there that are dumb.
Seiki and a few others make dumb-as-nails 4k screens for dirt cheap prices. Using a 39" one I got a year or so ago right now, and even then it was ~$285 pre tax. Not bad.
About the only thing I can ding it for is that some buttons on the remote aren't available for CEC, so I still have to use my RC6 remote and IR receiver on the Pi to control Kodi for all but the most basic functions.
Also, if you're looking for a 4K set, I'm not sure there are any out there that are dumb.