Hydrogen’s small molecular size facilitates permeation through many conventional materials, leading to leakage and potential embrittlement of metals. These characteristics create "unique" (read: expensive) engineering challenges.

And if you store it as a liquid that's when you enter the whole cryogenic problem, seeing it needs to be cooled to over - 225c

Even with advanced insulation, liquid hydrogen storage experiences unavoidable boil-off at rates of 0.3-3% per day, creating both economic and safety challenges.

And if you could make hydrogen via electrolysis, even with some uber wunderful unobtanium catalyst then you're still just waiting electricity that we can store far more efficiently in batteries (and with sodium batteries hitting the market there is going to be a huge revolution in battery economics and tech that will make lithium look like a drop in the ocean.

You would store it as a pressurized gas in this scenario. You would only use liquid hydrogen in specific situations.

https://www.youtube.com/watch?v=djg_l7cEtWg

https://hydrogenhouseproject.org/index.html

they clearly held some sort of gas fine for millions of years, so certainly they’re gonna store a bit of hydrogen too.

Not to rain on your parade, but hydrogen and natural gas aren't really comparable for storage. The natgas molecule is 8x heavier and MUCH larger than a molecule of hydrogen. Just on the size alone, hydrogen can slip through just about everything and needs to be stored at cryogenic temperatures. I don't think rock is going to be as good of a storage media as you'd assume.

Oh that makes sense.

We just don't have any natural gas production in Estonia lol. Perhaps the shale mines could be used. Unfortunately the biggest one had its permit extended till 2049 recently. Also I think they get filled with water naturally (they pump out a lot of dirty water), so I suppose the walls aren't actually completely sealed naturally.