zlacker

>These usually get neither an LED nor a switch

Lots of ThinkPads have «Microphone is muted» LED. Not exactly what's requested (and is bound to a software mute/unmute shortcut), but it's better than nothing regarding state of machine being observable with a quick glance.

>>throwa+(OP)
That one seems to be software controlled. I'm fairly sure I remember having the mic working with the mute LED lit, which was confusing. That was on a x1 carbon gen9.

>>mkj+G4
Correct, its usefulness depends on software working as expected (and not being tampered with)

    echo 1 | sudo tee /sys/devices/platform/thinkpad_acpi/leds/platform\:\:micmute/brightness 

is enough to turn the LED on without muting the mic.