The secret to hydrogen safety is assuming everything leaks at all times, and maintaining positive airflow everywhere that hydrogen is not wanted, so the concent

The secret to hydrogen safety is assuming everything leaks at all times, and maintaining positive airflow everywhere that hydrogen is not wanted, so the concentration cannot build up to the point where ignition is possible. You need to worry about material degradation mainly at high pressure where the material has to be very strong, and where the hydrogen is driven into the crystal structure, weakening it. At low pressure, ordinary aluminum is resistant to hydrogen degradation, and doesn't need to be strong. Whether liquid hydrogen is kept refrigerated below its boiling point, or kept well insulated but allowed to boil off, will depend on detailed engineering analysis. As the energy needed to produce it gets cheaper, the extra complication of keeping it too cold to boil gets less attractive. Maybe to refrigerate the tank, it needs to be above-ground so servicing is possible; but without, it can be wholly underground and thereby better insulated.