[x] that I haven't found an existing compatibility report for this game.
[x] that I have checked whether there are updates for my system available.
Symptoms
The game is playable but there are minor graphical glitches with shadows flickering and graphical detail (there was no difference between using proton-8.0-3c and experimental-bleeding-edge-8.0).
Workaround use Steam Launch command to force DX12 mode to fix the flickering: -force-d3d12
Forcing the game to launch in DX12 mode fixes the flickering issue (but the game is probably slightly too bright in forced DX12 mode)
Default DX11:
Forced DX12:
Notice that the DX12 is slightly brighter and at that distance the graffiti in DX11 is not visbile
Reproduction
Play through the very first section of the game until you get to the town
The first spot in the game where you can see the flickering issue is to run straight ahead to the town past the diner, then go left and look at the grafiti/wall next to the entrance to the school/gymnasium.
Video showing how to navigate to the stop:
I'm closing this issue because this appears to be a bug in the game, and not an issue specifically with Proton. I compared and found out that the shadow flickering occurs on Windows too at the same spots.
Compatibility Report
System Information
system_info.txt
I confirm:
Symptoms
The game is playable but there are minor graphical glitches with shadows flickering and graphical detail (there was no difference between using proton-8.0-3c and experimental-bleeding-edge-8.0).
Workaround use Steam Launch command to force DX12 mode to fix the flickering:
-force-d3d12Forcing the game to launch in DX12 mode fixes the flickering issue (but the game is probably slightly too bright in forced DX12 mode)
Default DX11:

Forced DX12:

Notice that the DX12 is slightly brighter and at that distance the graffiti in DX11 is not visbile
Reproduction
Video showing how to navigate to the stop:
moon.webm
Attaching a savefile of starting spot above when reaching the town:
The save file goes in /SteamLibrary/steamapps/compatdata/1147330/pfx/drive_c/users/steamuser/AppData/LocalLow/Lifeless Worlds/
Lifeless Worlds.zip
Including logs of playing up to the glitchy spot in the game:
steam-1147330-.zip