Submission linked report is from the UK which has had an underground hydrogen storage salt in dissolved salt caverns beneath Tesside since the 1970s (recently closed IIRC).

This method is of interest and development in Australia: Geoscience Australia explores storing hydrogen gas in Adavale Basin salt caverns - https://www.abc.net.au/news/rural/2026-02-22/geologists-dril...

and to China and the Saudis: Underground Hydrogen Storage in Salt Cavern: A Review of Advantages, Challenges, and Prospects - https://www.mdpi.com/2071-1050/17/13/5900