I've had good success with Sony professional displays and the costs were very reasonable (maybe ~300£ more than the equivalent consumer grade model). It's stock Android TV with no bullshit what-so-ever, and of course you can use a separate set-top-box via HDMI-CEC or even just set it to power on/off upon receiving an HDMI signal like a computer monitor.

CEC can switch inputs, and you can get a portable keyboard/mouse for input.

That LG one I posted above comes with a remote.