Hmmm. In terms of Joules to thrust, Hydrogen, driving a fuel cell, then driving a motor, probably via SMPS power supply, is really more efficient than just burning the fuel in an internal combustion engine?

Doesn't add up to me, though I can't find much reference on the subject. Cummins gives a brief explanation implying the fuel cell powertrain can be more efficient in specific scenarios where the load is often removed from the drive (Like maybe cars / trucks when coasting), and regenerative braking can be used in deceleration (Again applicable to cars) but neither of those scenarios exists for most things airborne. In healthy flight, carrying any weight, the load is persistent, and regenerative braking would only be possible to some extent, only on landing.

Agree hydrogen electric for trucks, yay.

https://www.cummins.com/news/2022/01/27/hydrogen-internal-combustion-engines-and-hydrogen-fuel-cells