Compatibility Report

I tested Proton 3.7-8. I haven't got any "Out of Sync error" with this version but I did have some crashes and hangs when playing online.
I experienced fewer crashes when using PROTON_FORCE_LARGE_ADDRESS_AWARE=1.
So far this configuration is the most stable for playing online.

I tested Proton 3.7-8. I haven't got any "Out of Sync error" with this version but I did have some crashes and hangs when playing online. I experienced fewer crashes when using PROTON_FORCE_LARGE_ADDRESS_AWARE=1. So far this configuration is the most stable for playing online.

After playing multi-player with no stability issues for years, I suddenly started getting 'Out of Sync' errors on every match a couple of months ago. I tried your suggestions and it has been perfectly stable for the last 8 or 9 multi-player games I've played. Thank you!

I confirm @pnguyen9 observations, the multiplayer game is more stable after the aforementioned manual dll copy/pasting but still end up desyncing.
Many games are concerned by this desync issue:

• https://github.com/ValveSoftware/Proton/issues/6568
• https://github.com/ValveSoftware/Proton/issues/2907
• https://github.com/ValveSoftware/Proton/issues/3189

The main cause of the problem is, apparently, well known:
https://www.codeweavers.com/blog/rbernon/2022/9/12/ucrtcringedll-reverse-engineering-ucrtbasedll-for-pain-and-non-profit

@PHLF I've had the same desync issue while playing Dawn of War II and its expansions (Chaos Rising, Retribution) in the past, but it seems to be so much more stable by applying these two fixes:

• Download and use Proton 6.1 GE-2 (greatly improved stability but still had it happen once in the past).
• The aforementioned COH2 fix.

So far, I haven't had another desync (yet), but I haven't tried with the other games, so I don't know whether or not it would also help.

I've experimented this issue with my friend today we try the PROTON_FORCE_LARGE_ADDRESS_AWARE=1 arg and the COH2 fix but we still have the Out of Sync error

To fix the de-sync issue when playing multiplayer you can just install vcrun2005 through Protontricks. Someone wrote a guide and posted it here.

EDIT: For what it's worth, if you're trying to play this game in the modern age with a 4K resolution display you will find that all the UI elements are really small. The best solution to this that I've found is to use gamescope and up-scale to 4K from 1080p. This works great for me under Fedora 42:

env -u LD_PRELOAD gamescope -h 1080 -H 2160 -r 130 --scaler integer --filter fsr --fsr-sharpness 0 --backend wayland --expose-wayland --steam --hdr-enabled --fullscreen -- env LD_PRELOAD="${LD_PRELOAD}" gamemoderun %command% -forcehighpoly -nomovies

A brief explanation of what's going on here:

• env -u LD_PRELOAD - without this the steam overlay doesn't work
• gamescope - upscales from 1080p to 2160p using FSR. This scales the UI elements such as text and cursor as well so it actually ends up being a better option than setting a native 2160p in the game itself.
• -r 130 - I try limiting the the frame rate but that causes microstuttering unless I also set screennovsync=1 in the game's Local.ini. Setting the limiter slightly higher than the screen refresh rate seems to help though.
• gamemoderun - This gives the game binary priority and prevents some incorrect warnings about the game hanging.
• Not used above but it is possible to scale the cursor separately from other game assets by doing: --force-grab-cursor --cursor-scale-height <n> where <n> is either a multiple or an even divisor of the resolution, so in this case: 540, 1080, 2160.
• For this to work properly one also needs to run: setcap 'CAP_SYS_NICE=eip' $(which gamescope)