

Looks like the compatibility between this game and the Steamdeck have improved drastically!

Installed d3dcompiler_47
mapped game specific keyboard inputs
The game does not launch without d3dcompiler_47 installed on the prefix

d3dcompiler_47
your graphics card does not support directX 12 features the game requires

protontricks ... d3dcompiler_47
Played GOG version with Proton 7.0-1 and install d3dcompiler_47.

You have to install protontricks: https://github.com/Matoking/protontricks Open your Steam directory: STEAM/steamapps/compatdata/1305720 Right click>open in terminal and then install d3dcompiler_47: protontricks 1305720 d3dcompiler_47
Could not conventionally escape from fullscreen (such as with Alt-Tab).
For those who are using the Flatpak package of Steam, the equivalent incantation to that discussed by others is:
flatpak install flathub com.valvesoftware.Steam.Utility.protontricks
flatpak run --command=protontricks com.valvesoftware.Steam --no-runtime 1305720 d3dcompiler_47

Try to start the game once to have its compatdata folder set up.
Then via terminal run winecfg and set the Windows version to Windows 10:
WINEPREFIX=$HOME/.steam/steam/steamapps/compatdata/1305720/pfx winecfg
And run this command to fix the shader compile error (need to install protontricks if you don’t have it yet):
protontricks 1305720 d3dcompiler_47
WINEPREFIX=$HOME/.steam/steam/steamapps/compatdata/1305720/pfx ~/bin/winetricks d3dcompiler_47

By default, complains about Windows10. Then 'Your graphics card does not support the DirectX 12 features the game requires'
I have used winecfg to set windows version to win10 which allows to go further I have used winetricks to install d3dcompiler_47. But it still fails
Note: Proton v5.0-9
Before the game fully starts it will crash with the following error:
ZLDX12Shader: Failed to compile a cs_5_1 shader
This will fix it:
protontricks 1305720 d3dcompiler_47
I followed chrikle guide and it worked! Had to do some minor adjustments to the last command though due to conflicts with the wine version I have installed. To specify the exact wine version used by Proton execute the winetricks command like this:
WINE=$HOME/.steam/steam/steamapps/common/Proton\ 5.0/dist/bin/wine LD_LIBRARY_PATH=$HOME/.steam/steam/steamapps/common/Proton\ 5.0/dist/lib64 WINEPREFIX=$HOME/.steam/steam/steamapps/compatdata/1305720/pfx ~/bin/winetricks d3dcompiler_47
Update Proton to Version 5.0-8 in Steam
Get the Proton Prefix for Dolores --> it is 1305720 (you get it if you look at the Url of the Showpage (if it is not shown you can activate it in the Steam Options)
Switch proton (wine) to Windows 10: run: WINEPREFIX=$HOME/.steam/steam/steamapps/compatdata/1305720/pfx winecfg
In the Dialog: Windows Version to Windows 10
Install d3dcompiler_47 with winetricks:
On Ubuntu 18.04 you need an actual winetricks Version. Installation: run: mkdir ~/bin wget http://winetricks.org/winetricks -O ~/bin/winetricks chmod +x ~/bin/winetricks
d3dcompiler_47: run: WINEPREFIX=$HOME/.steam/steam/steamapps/compatdata/1305720/pfx ~/bin/winetricks d3dcompiler_47
Shows black game window briefly then terminates with a "Critical Error!" stating "ZLDX12Shader: Failed to compile a cs_5_1 shader".
Error message: "You need at least Windows 10"
Window'ish error popup saying "Your graphics card does not support the DirectX 12 features the game requires."
As others have said, you get an error at launch: "Your graphics card does not support DX12"

Fails to start, only shows an error message
The error message says: Your graphics card does not support the DirectX 12 features the game requires.