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
Where 20920 is the game id.
First you 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
Edit: ooohh is this Tarkov and SPT?!
I don't know the full details but I have worked with the following scenario with NFS Heat and it's Mod Manager Frosty.
So, first I ran the vanilla game, made sure it works and let the game's Proton profile be created.
Then, I used to ProtonTricks via double clicking the mod manager .exe file and launching it via ProtonTricks and selected the game's Proton profile.
Ideally, now the modmanager.exe will run within the game's Proton profile and have access to the files the game created within the Proton profile etc.
Sometimes, (like with NFS Heat and Frosty), the mod manager would need additional files within the Proton profile which the game did not need. For example, with Frosty, I needed dotNET 8/9/10 depending on the build of Frosty which NFS Heat did not. Which is why Frosty did not launch for me even when NFS Heat worked fine within the same Proton profile.
ProtonTricks can be used to add these dependencies too into the game's Proton profile.
Edit: Also, the compatdata folder might be wrong imo.
Use ProtonTricks, select Tarkov's Proton profile, then select "default profile" and in the next window, click on "Browse the files within the Proton profile" or something like that. This will open the actual folder for the Proton profile for Tarkov