Interesting. The linux driver version shows 390.87 as the latest. However, if you select Windows, it will show 399.24 as the newest. Where did you install the driver from? I'm just looking on nvidia's website, perhaps they don't update it as often as I would think (at least not for Linux).
I use the method of driver installation outlined here:
The 396.51 driver I am using is available for download from Nvidia using the advanced search here:
(Be sure to choose "ALL" under Recommended/Beta)
I've been reading that there are certain Nvidia driver versions that work, and the rest don't currently. 396.51 is listed as working. So for anyone having trouble make sure that this is the driver you have installed. Note: It isn't the newest driver in the 396 series.
It's been 2 and a 1/2 weeks, and I've played an embarassing amount of GalCiv3. It is stable for the most part. I do occasionally get a "freeze" - i'd say no more than once every 8-10 hours. That said, I get the same freeze in Windows, and due to some historical problems I suspect my video card is the culprit, not Proton/Steamplay.
Everyone having problems: I enabled Steamplay for all games, and I am running this through Steam. I never did the download and compile of Proton from github. I just enabled Steamplay beta for all games, added /nolauncher to the command line startup, and disabled multi monitor. Then boom. Apart from Blackholes being invisible everything else is working.
Since my initial post I have run in to 1 other issue. When the AI attacks me, if I have defending legions, then the game doesn't get past the "Legion Placement" screen. It just looks like it is waiting for something forever (let it run over night to see if it was just taking a long time). I have got around this by clicking "Quick Battle" - which I have to do quickly, else it stops responding. This is not a problem when I attack the AI and they have defending legions, only when they attack me and I have defending legions.