I am not a hardware engineer or anything of the sort. My laptop has a slide shutter over the webcam, but this obviously does nothing about the microphone. How difficult/error prone would it be for the power signals to the microphone and camera to be individual wires/traces and have a physical switch that breaks the power or data connection physically? Surely these are very low voltage so the switch could be like the iphone mute switch?

My Framework 13 has this - 2 physical switches next to the camera. I would assume (but haven't checked), that they physically disconnect the camera/mic.

The Framework laptop does this for both microphone and webcam, and there are privacy focused Android phones which also have a microphone switch which cuts the power to the microphone. It's definitely possible.