IMO, the reality is that these plants will never convert to anything other than natural gas and will eventually be shut down, still running on natural gas.
Hydrogen is not a fuel, it's an energy storage mechanism, and not a very good one at that. If you're going to store energy there's much more efficient and/or cheaper ways of doing it.
Natural gas is still a good fuel but I don't think anyone in the US at least is under any illusion that these will ever run on anything other than natural gas.
The big problem with the hydrogen economy is not the conversion of the gas plants, it is having enough wind to generate the hydrogen in the first place. You need excess wind capacity to make hydrogen, and no private venture will invest into wind turbines that aren’t needed. Without a strong government hand shaping this market it will not happen.
If you are looking for a skeptical take, here’s a good one: https://cleantechnica.com/2021/12/06/new-eu-hydrogen-policy-...
Edit: the problem I am remembering is that hydrogen actually degrades the metals used in pipelines (https://www.hollandsentinel.com/story/opinion/columns/2021/0...) so I don’t see how any of this infrastructure is useful at all for hydrogen.
You can walk right into one if you are not careful - which is why you might see people walking with brooms in front of them around hydrogen equipment. :)
The real problem is the fact that environmentalists tend to hate dams, especially large hydro projects, so there's a major political battle on top of finding funding for these kinds of capital-intensive projects.
...unless you go radical? https://www.anu.edu.au/news/all-news/anu-finds-530000-potent...