Has the hydrogen storage problem been solved yet?
Last time I checked it needs to be stored in cryo / pressure vessel and it also leaks through steel and ruins its structural properties in the process.
> Has the hydrogen storage problem been solved yet?
No. Not for using Hydrogen for transportation. People have been trying to use Hydrogen for transportation for more than 50 years. These people are trying to bend the laws of physics. And there are a lot of con artists in the mix who prey on the gullible. See the convicted fraudster Trevor Milton of Nikola fame.
We store hydrogen all the time for industrial processes. It's not some super science, it's just expensive.
There are some innovation like hydrogen paste but it’s not going to be useful for a combustion engine cycle.