Great, so you're already halfway there! You may be right on the temp sensor and the gas detector would probably be spotty too. I was thinking you could glue some magnets to the knobs and use a hall effects sensor nearby to map their position, but that would take some tinkering and I personally haven't done anything like that.

But you mentioned you already have a camera pointed at it, you could add Frigate to Home Assistant and use object detection to notify you about events such as 'knob turned' or 'panel glowing' for flame detection or even just have it compare snapshots every x minutes and notify you of any change at all. Then you still always have the camera for visual backup as well.