As per the linked FAQ,
What platforms will Sid Meier’s Civilization VII be available on?
Sid Meier’s Civilization VII will be available on PS5, PS4, Xbox Series X|S, Xbox One, Nintendo Switch, and PC via Steam (which also supports Mac and Linux) and the Epic Games Store.
The Steam store (preorder) listing shows all three platform icons so I’m guessing they’re not just talking about making it work with Proton.
No mention yet of Aspyr (who ported Civ 5 & 6) as far as I can see.
I hope it will release on GoG at some point
Gog sucks nuts on Linux though. It’s such a pain in the ass to get my Gog games working in Lutris that I opted to install Gog Galaxy as a non-Steam game and then install my Gog games through that.
I never had much luck with Lutris either. Try Heroic games launcher. It’s fantastic with Linux and GoG