Diesel engines can be converted to run on 90% hydrogen
https://www.technology.org/2022/10/08/diesel-engines-can-be-converted-to-run-on-90-hydrogen/
Wow, that actually looks fairly promising. Usually these type of articles are very pie-in-the-sky. I know it is possible to run regular ICE on hydrogen, but last I looked the efficiency was far less than electric fuel cells.