I don’t know how much research/traction this idea has, but I’ve heard of a reverse hybrid system that seems to be a good solution in my mind. The electric engine operates the drivetrain, and the combustion engines runs continuously at its most efficient configuration to act as a generator for the electric engine

This is a very common setup, usually it’s diesel-electric. Diesel trains often work like this, it’s also used on submarines, ships, trucks, etc.