I heard cars use a network of microcontrollers because operating systems are not real-time enough (process timesharing). They would probably only use an OS for

I heard cars use a network of microcontrollers because operating systems are not real-time enough (process timesharing). They would probably only use an OS for the in-car display, like Tesla does (Ubuntu), which obviously isn't (shouldn't be) critical for the other functions of the car.