Iirc, in the earlier days of LCD tvs, the ones meant for digital signage sometimes had different color calibration, and also sometimes had weaker processors than their consumer bretheren because they weren't really meant to display high-framerate motion content, and were mainly used for static images. A friend's dad picked up a few for cheap when their employer was updating some of the ones they used for digital signage, and they struggled with some types of 1080P content, especially when the images were messy and rapidly changing (think close up tracking shot of a soccer game.)

Not sure how relevant that is today, but likely still something to watch out for especially if you're looking for a cheaper dumb TV. Also, if you're getting a used digital signage TV, if you can try to run through some basic color and motion video tests on it before you buy it; mostly to check for burn-in and backlight quality.

Also, are there decent OLED dumb TV options available yet? I rarely watch anything on my TV, so when I do it's generally something more 'special' and I rather like the gamut that OLEDs offer for those occasions.

Sony and Samsung were the two TV manufacturers that first introduced this technology of automatic content recognition to my knowledge.