I did this using Rog Ally running Bazzite but the steps for Steamdeck should be identical. Keep in mind that you will not be able to do online races with this method, because the anti cheat engine will not work!
Download the iRacingInstaller and save it to $HOME/.steam/steam/steamapps/common/iRacing/.
Open the file $HOME/.steam/steam/steamapps/common/iRacing/StartServiceAndPlayNow.bat and add this line directly behind @ECHO OFF:
iRacingInstaller_win_2025.05.06.01.exeThis will start the iRacing installer in the right Proton instance.
Start the iRacing from Steam and run the installer.
After installing it, edit the file $HOME/.steam/steam/steamapps/common/iRacing/StartServiceAndPlayNow.bat again. This time add the following four lines after @ECHO OFF:
cd /d "C:\Program Files (x86)\iRacing\"
start /B Start_iRacingService.bat
start /B ui\iRacingUI.exe
cmd /k
The last command is for keeping the Window open. The main change is add /d to the cd command. Otherwise the current method will not start.
This is the installation folder of iRacing in case you need it:
~/.steam/steam/steamapps/compatdata/266410/pfx/dosdevices/c:/Program Files (x86)/iRacing.
Have fun!