The Mirai is 196 inches long (same as a Model S or BMW 5 series) yet has less than 10 cu ft of trunk space. The volume required to fit all the hydrogen fuel cell components is massive. It's not especially practical as a result. Even if there was a refueling network, it's not like you're going to take it camping or road trip with such a small trunk, and for an around town grocery runner it's on the large side.

It's not like there's a good source of hydrogen that doesn't come from electricity generation anyway. It's "just" a different take on the battery, one that appears to be mostly worse other than charge times.

Most hydrogen isn't from electrolysis of water. It's mostly made commercially from natural gas.

Right, yes, sorry I meant no potential green sources of hydrogen that don't come from electrolysis.

“They just need a refueling network” - case in point, wildly impractical to buy one today.