so the point about curtailment is good, but it's a slightly one sided perspective on the question and the question about financial viability rather depends on the market that you are looking at. Where there is the vehicle demand, people are already beginning to install renewables to support the electrolysers, not electrolyses to catch the constrained power from installed renewables.
In the natural gas/heating and industrial processes, it's a way off competitive because of the extreme low price of natural gas, however policies that reward carbon reduction are starting to motivate companies like Shell and Phillips 66 to install electrolyses rather than using traditional SMR hydrogen in some parts of their supply chain. so it's expensive but there is so much of the final cost of the fuel made up by tax, motorists won't notice.
In the pure road transport sector it's possibly a bit closer, their it's up against a much higher comparable cost (petrol and diesel) and specifically in things like captive fleets a cost of U$7/kg is about the point where it becomes the same operational cost as diesel (because of the high energy density). But in these fleets, it needs the fleet in the first place to get to the scale to hit that price.
So on the transport side the restricting factor is really the vehicles, preferably large ones that use a lot, which is fortunately what hydrogen is best at. Enough density of busses/trucks/taxis in an area and locally hydrogen can hit diesel parity in 5-10 years, once it does that in one location it'll start spreading.
Where there is the vehicle demand, people are already installing renewables to support the electrolyses.
industrial heat, maybe 15-20 years, but if it takes off in transport more quickly this will likely shorten as the electrolyser producer ramp up to scale and make gains on the learning curve, which will likely be faster than we currently see on batteries in the first instance as most of the PEM manufacturers are effectively hand building at the moment.
The investments various governments put in as a part of COVID recovery could shorten these time scales down to closer to the 5 years slot, but not really any closer and then only for the environments where hydrogen is up against high value or high energy density alternatives.
there isn't really a single source on hydrogen better than the report you found but maybe look here for a very UK based set of analyses:
CCC review
hydrogen in a low carbon economy
Heavy duty transport