Yep, a commercial display is what OP is looking for. You won’t get fancy stuff like high framerates or digital audio processing, and they cost a bit more as many of them are meant to be on 24/7/365, but there are no apps installed. They’ll have network connectivity, but only so you can manage them.
Be careful when buying commercial displays for digital signage, some do not have speakers built in, though they should still have a 3.5mm and/or optical out and you can always strip the audio from an hdmi cable.
My guy, robot mowers have been around for some time now. The catch is you need to bury a guide wire around the perimeter of the area the mower is meant to cut. Or at least that was the case the last time I looked into getting one.