The world produces and uses 700 cubic kilometers (at STP) of hydrogen annually. Hydrogen has been used on a mass scale industrially since the 1800s. The US has over 1000 miles of hydrogen pipelines.
There are obviously off the shelf components for dealing with hydrogen. This is not some hand wringing unsolved problem.
It can be used there are just better, cheaper options. Same for compressed air, molten salt, tidal power or a litany of other working tech that doesnt hit the right price/performance point.
Better cheaper options for seasonal leveling of a 100% renewable grid, or backing up the grid against rare prolonged renewable outages? Pray tell me about these.
There are obviously off the shelf components for dealing with hydrogen. This is not some hand wringing unsolved problem.