"pumped hydro isn’t available in Germany on the necessary scale. "

Not actually true. I would recommend looking at the ANU pumped hydro greenfield atlas and look at Europe, there's an enormous amount of closed-loop, off-river pumped hydro resource available. You aren't alone in thinking otherwise, but like everyone else who thinks so, you aren't correct.

https://re100.anu.edu.au/#share=g-d39a5688446926d55bf059716f828959

Second, grid interconnects in various directions outside of Europe are going to bring more and more green electricity into Europe. Georgia to Romania HVDC approached to bring Carpathian renewable electricity to Europe. Morocco to UK HVDC in progress. Israel to Greece HVDC under constructon. Tunisia to Sicily HVDC under construction. EU to Canada in early days.

One time zone's peak is another time zone's lull.

And what seasonal storage is required for 50 to 100 year dunkelflaute is better in the form of captured anthropogenic biomethane, diverting a climate problem to an energy solution, rather than making an incredibly leaky molecule at great expense.