I see what you mean. Propane conversions are way less intrusive than EV conversions. Propane is not very heavy or bulky, and you can use the same engine in many cases. I'm no expert on it but that's what I've gathered.

I think hydrogen and other chemical power sources have the best potential to replace fossil fuels. I think Toyota is betting big on hydrogen, and they know a thing or two about EVs. Researchers are looking at synthetic hydrocarbons now too. Eventually, that may become the best option.