The key is sufficiently cheap electrolysers. They are below $300/kW now. The other steps (if any) have higher capital cost/energy cost ratios, so they can be done when energy is more expensive.
Today, in Finland, renewables produced between 0,2 GW and 1,5 GW.
Does that mean I would need $450M (1,5 GW * $300/kW) in electrolysers to soak up all that power?
For simplicity's sake, let's say output averages 1GW over 24 hours? What do I get for the day with my $450M electrolysis plant?
For Finland, the 2030 assumptions number (for "synthetic baseload" from renewables + storage) is just under their "EPR" number (which may be a bit optimistic, given your experience with an EPR). As I said, Finland is a tough case for renewables. The solution has > 400 MW each of solar and wind, and 110 MW of electrolysers (to provide 100 MW of synthetic baseload).
I got Average system cost [EUR/MWh]: 101.9 which is more than nuclear, when solving for renewables + storage + hydrogen.
But as I also said elsewhere in these comments, this just means Finland (and other nearby countries at high latitude and without good wind resources) will become energy ghettos. They will lose their energy intensive industries. You will not be able to compete in such industries with countries where solar seasonality is low and insolation is very high. This means your energy consumption per capita will be depressed. Can a nuclear industry survive powering a handful of such disadvantaged countries? Maybe they'll just import energy from elsewhere (hydrogen can be piped like natural gas; while it has less energy per unit volume it also has considerably lower viscosity, reducing pumping costs.)