Oh, Thanks for testing it on Linux! That's really valuable to know.
Regarding the controls:
• Yes, C is for landing, Alt works with zero thrust (both options are blocked in the current build). Use Space + Shift. It is boosted flap and it allows you to fly faster (if you have stamina enough).
• For the stabilization use Q/E. This will roll you along the longitudinal axis. The physics model uses "roll-to-turn". Stabilization is intentionally physics-based rather than automatic, but if multiple players find it confusing I'll definitely will add more of tutorial phases.
Yeah, "Beat the Storm" is brutal. And this is only the first phase in the Arena-mode.)