I know of a couple of smaller shipping companies running on propane for their shipping trucks.
As for diesel, it might still be possible. I am not an engine designer or a mechanic but I do know that much of the catalytic “stuff” is designed to burn off particulates post combustion. Perhaps a high enough powered laser can burn these within the diesel engine before it is exhausted. Not sure that would provide any additional power but it could treat the exhaust. Perhaps enough to remove the catalytic converters and thus regain the power lost to them???
Just wondering out loud here.
In this example, it is possible. But I don't believe incomplete combustion is a problem in propane fueled engines.
Still sounds like an expensive solution in search of a problem.
I doubt the complexity of adding an entire additional system to diesel engines would be an acceptable trade-off if the only benefit was being able to eliminate the catalytic converters.
A system such as this makes perfect sense for an engine with spark-induced combustion. You already need an ignition system, so replacing spark-plugs, coils, etc. with a different means of ignition does not add an entirely new system to the engine.