Running games through Steam's Proton is great. But what if there is a secondary exe or configuration application bundled with the game? How can you launch it if Steam itself only launches the game?
Simply run this command in a terminal:
cd /path/to/steam/steamapps/compatdata/20920/pfx STEAM_COMPAT_DATA_PATH="/path/to/steam/steamapps/compatdata/20920" WINEPREFIX=$PWD \ "$HOME/.steam/root/steamapps/common/Proton 5.0/proton" run ./drive_c/path/to/custom_application.exe
20920 is the game id.
cd (change directory) to the proton prefix in question. If you don't have any custom steam libraries it likely will all be within your home directory. To find it easier you may run
find . | grep compatdata from
~/ and when you find it,
cd to it.
Real world example:
cd /media/michael/SSDGAMES/steam/steamapps/compatdata/20920/pfx STEAM_COMPAT_DATA_PATH="/media/michael/SSDGAMES/steam/steamapps/compatdata/20920" WINEPREFIX=$PWD \ "/home/michael/.steam/root/steamapps/common/Proton 5.0/proton" run \ ./drive_c/flawless/FlawlessWidescreen.exe
Someone in the comments below created a bash script that makes this easier: https://gist.github.com/michaelbutler/f364276f4030c5f449252f2c4d960bd2?permalink_comment_id=3921629#gistcomment-3921629
Now I am getting a weird error where the command returns that the proton file does not exist.
bash: /home/yourlocalmedic/.local/share/Steam/compatibilitytools.d/Proton-6.16-GE-1/proton/: No such file or directory
I am certain that a typo is not being made.