Desalinating seawater can consume huge amounts of surplus power, not necessarily stable.

(Extracting lithium, uranium, thorium, gold from the brine could be a bonus step.)

There aren't a lot of places in the north where you'd need desalination; streams suffice for thin populations. Elsewhere in the world, I can see that.

Indeed so! Closer to tropics, such places abound though. "Excess" solar generation can go there.

Unlike in the north, where there's no excess.

Honestly, I've been looking at just that in combination with agricultural/reforestation techs for a couple years now. Australia is way bigger than the maps make it look, Africa too. Find an area near a volcano you can rob and grind for soil and you'll do very well once energy is cheap enough. Due to climate change - esp in future - many locations will require heat control via shade (not too dense solar farms) and evaporation (of sea water on cardboard in one trial.) No doubt the current food shortage is temporary, the solutions emerge inevitably from cheaper energy (and AI farm equipment.)