Cranked all the graphics settings to low, except that I did keep resolution at 1280x800. Never finishes loading a map.

Turned on Steam's performance monitor to its fullest to see what was going on while it was trying to load. Both GE-Proton and Native Runtime, it simply wants too much RAM. CPU-side was taking up 12GiB, GPU-side wanted 5GiB, and...well, do the math, there are only 16GiB! So it never even loads. It's funny, I never think of this game as being that much of a memory hog on Windows, but I'm also playing there on a beefy desktop most of the time.

At any rate, I'm pretty sure that's why so few people have luck with this on the Steam Deck. Maybe it could be mitigated by increasing the Linux swap area, but that's rarely a good idea for performance.

I'd love to see Colossal Order and/or Paradox see what can be done about this, but I don't hold out much hope.