And if you don't have salt domes, you can use more laboriously excavated caverns in hard rock. This would still be an order of magnitude cheaper than batteries per unit of storage capacity.

But, more expensive than other energy storage methods. Sometimes though you really want to store hydrogen, not just any old energy. A disused mineshaft often suffices. The world is absolutely perforated with disused mineshafts, that only need a lid.

A buried LH2 tank can have very, very good insulation. You probably want to flare off or re-liquify any boil-off, because H2 has, all told, something approaching 200x CO2's GHG potential.

More like 11x (depending on the timescale). Hydrogen itself has no GHG potential (no IR absorption), but it does soak up OH radicals that would otherwise destroy methane, so it acts as an indirect methane source.

https://newatlas.com/environment/hydrogen-greenhouse-gas/