"He’s like Dave Grohl’s younger brother."
Liquid hydrogen on planes is a cool proof of concept but not much more. The volumetric energy density of liquid hydrogen is about 1/5 that of jet fuel and the thermal efficiency of the engine will remain essentially constant whether burning jet fuel or hydrogen. This means that we would need fuel tanks that have 4.4x the capacity to maintain the same range.
The energy density is what it is and cannot change. The thermal efficiency of the engine is subject to incremental improvement but don't expect anything major, this is mature tech operating close to theoretical limits. Hydrogen has all kinds of great applications but aviation likely isn't one. But hey, s-curves on top of s-curves, maybe we discover something we never thought possible.