With regard to the first paper, fair enough, it is over my head too. This paper, also from the Sandia National Labs looks at various polymers and finds two thermoplastics whose physical properties survive exposure to high pressure hydrogen, osti.gov. It's also dense, but slightly easier for me than the first. It's clear not all polymers are equal and two thermoplastics look like good candidates for containing high-pressure hydrogen. I see no reason why some form of thermoplastic couldn't line a metal container any preferred shape.
Characterization of the polymers before and after exposure helped with establishing that relationship, with respect to high pressure exposure to hydrogen. The two thermoplastics investigated, have not shown any significant change in major physical properties such as Tg, modulus, and tensile strength
I don't know why the second link wouldn't work for you. Sorry, I remember another link I posted didn't work for you although it did for another reader. Here's the citation at the head of the paper which you could Google:
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REVIEW article
Front. Energy Res., 09 April 2021
Sec. Hydrogen Storage and Production
doi.org
Room Temperature Metal Hydrides for Stationary and Heat Storage Applications: A Review
 Poojan Modi† and  Kondo-Francois Aguey-Zinsou*
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