Hello @sknaumov, please add PROTON_LOG=1 %command% to the game's launch options and check if running the game generates ~/steam-215930.log. If it does, please drag and drop the generated log into the comment box.
Updated issue description, attached proton log. With 4.11-7 (or whatever version was the latest proton in Steam up to Nov 9) the game was perfectly playable. The only inconvenience was that I had to manually fix CD-key issue that it not present in native windows or linux ports (but native linux port no longer works - see https://help.steampowered.com/en/wizard/HelpRequest/HT-HGHP-PRPQ-C2P9)
Update: Proton 5.0-5 (or earlier) fixed the issue with registration key (there is no need anymore to enter it manually via regedit like described here: https://steamcommunity.com/app/215930/discussions/0/1814296273132304445/). But the game still crashes as described in this ticket. I also tried all the other available proton versions (4.11-13, 4.2-9, 3.16-9, 3.7-8) and the game crashes with all of them.
On the other hand, I came up with a workaround - if I go to tactic mode, then back to strategic map, and only then start game clock, there is no crash (tried on 4.11-13 and 5.0-5). But again, this crash is not specific only to one saved game and started to happen immediately after proton upgrade.
The most problematic save game with 100% crash reproducibility is attached SaveGame07.sav.log - just strip .log extension.
The game has "native" linux mode and is shown in Steam as "supported under steamOS", but under the hood it is just a wine script. It worked fine on Ubuntu-16.04, but on 18.04 it ceased to work, that's why I'm trying to use proton.
Compatibility Report
System Information
I confirm:
steam-215930.log
Symptoms
Game starts, I load a saved game, and when resume game clock from pause, it almost immediately crashes with any save I tried with 100% reproducibility. It started to happen immediately after Steam pushed new (4.11-8) proton version. Original problem report: https://help.steampowered.com/en/wizard/HelpRequest/HT-HGHP-PRPQ-C2P9
Reproduction