I had a manual Acura Integra when I was younger and I installed a remote start on it because shops refused to (because it's dangerous af).
Anyways, the clutch pedal simply presses a little button when it is all the way up. All I had to do is bridge the two wires going into that button and it would start without the clutch pressed.
Amazingly I only ever tried to remote start it while in gear once. It retries 3 times so it jumped forward 3 times. About a foot each time, but didn't hit anything thankfully.
I always wanted to add a sensor to the shifter so it'd only bypass the clutch sensor when in neutral, but I never got around to doing it.