I had a diesel car that I once drove with no alternator and no battery: started off a jump and drove to the auto parts store. Radio, windows, and lights were dead, but the car drove fine.
Fond memories of my Merceded W124. You could rip the engine out of the car and it would go on and on. No electricity for motor management required whatsoever.
Yeah - I remember when I was a volunteer firefighter - if you parked a fire truck in an atmosphere that was filled with combustible gasses, the engine would not shut off.
The trucks were equipped with some type of an emergency throw should that situation ever arise. We never had to use it in my time there.
I still own a MB with OM616 [1] engine. It does not need an alternator when it runs. Even to turn fuel supply on/off it uses mechanical valve which is on the dashboard. It turns 40 this year but it starts in a split second even in cold winter.
Diesel ignights via compression and does not require external ignition. For this reason, they can 'run away' and rev until they explode if somehow given too much fuel as the result of a failed injector or oil leak from the turbo that feeds the combustion cycle. The yt videos are intense.