The world uses many millions of tons of hydrogen a year. There are already 1600 miles of hydrogen pipeline in the US. So, while materials must be chosen carefully, materials compatible with hydrogen obviously exist.
Transportation is not the only, or even a particularly favorable, use case for hydrogen. Pointing to it to paint all hydrogen uses as inadvisable is not honest, especially in a thread where we're talking about reduction of iron ore, not cars.
Hydrogen is a greenhouse gas in this sense: hydrogen consumes OH radicals in the atmosphere which would otherwise go to destroying methane. So, indirectly, hydrogen causes warming by reducing destruction of methane. The effect is not large, however. Carbon monoxide has a similar indirect effect.
And it has a tendency to leak through most materials.
https://planetforlife.com/h2/h2swiss.html#:~:text=Hydrogen%2....
"B&E estimates that a liquid hydrogen tank designed for automobile use will loose about 5% of its capacity every day, which is to say that all of it will be gone in 20 days. Losses of this magnitude are acceptable for, say, a taxicab fleet, but unacceptable to most people."
Also new to me that it's a greenhouse gas: "Hydrogen cannot be vented to the atmosphere because it is an explosion hazard and because it is a greenhouse gas. The vented hydrogen must be burned. A continuously running gas stove with one burner set to "medium" would do it."