I was in a similar position earlier this year. Problem was most non smart TVs were business grade and very expensive. Ended up with a Samsung Smart TV but didn't hook it up to the Internet. Fits my needs and remote is only ever used for changing HDMI devices. It boots up in about 10 seconds.

What you want is a "public display".

Yes. They make them for commercial use, like the signs at fast food.

LG C1 is "smart", but satisfies your other criteria. It has been replaced with newer models, but I imagine the user experience must be similar.

I haven't even seen it's smart functions the whole time I've had it. I press a button on the Apple TV remote and a few seconds later the TV is displaying the Apple TV menu (connected via HDMI through a receiver). No menus to navigate and no ads that I've ever seen, though the first thing I did when I got it was disable all the "suggestions".

I just got a Hisense that’s google tv but in setup I had the option to configure it as just cable and inputs.

I got the U7 series. I don’t know if this feature is consistent across all google tvs or all Hisense tvs or what, but I’ve given you somewhere to start at least.

I've got a 55" from Westinghouse that's probably a decade old by now. It technically has some half-baked smart functions, but they're more like fixed apps than anything where you can install/update/change. It never gets connected though, just used as a monitor for whatever is attached. Cheap off-bramd type boxes are not bad if you're just looking for an output. Lots of times they don't have the time and resources to put into making some big infrastructure and app catalog, so they just focus on making the screen and inputs work.