Now that Valve’s Proton project has been launched I hope that there is at least one interested developer within the Warhorse team, who can make this game initially compatible after the download.
Proton compatibility report for Kingdom Come: Deliverance
According to the compatibility report you have to copy a whole folder win64shared to win64 or at least two DLL files, d3dcompiler_46.dll and d3dcompiler_47.dll to make the game work.
Since Linux support has been promised to backers and hasn’t been given, at least I expect you to do this little favor to your backers, to make this game compatible so they can play the game just like a native one without fiddling with DLLs.
I can confirm that
cp ~/.steam/steam/steamapps/common/KingdomComeDeliverance/Bin/Win64Shared/* \
was sufficient on my system to make the game runnable with Proton, when started with the following start option in Steam:
It is running fine but seems to have shader compilation hangs. Though, this should be fixable. (By adding a shader precompile feature to proton and ship precompiled shaders which might already be planned or in the development branch)