NFS Most Wanted (2005) on my Steam Deck

I added Need for Speed: Most Wanted (2005) to Steam as a non-Steam game on my Deck. The repack included a _SteamDeckFix folder and instructions to set WINEDLLOVERRIDES"dinput8,d3dx9_26,d3dx9_43=n,b" %command%= as a launch option. I did all that, but the game refused to start.

Protontricks. Install it via Flatpak if you have not already:

flatpak install flathub com.github.Matoking.protontricks

Find your game's App ID and install the d3dx9 verb:

flatpak run com.github.Matoking.protontricks -l | grep -i "most wanted"
flatpak run com.github.Matoking.protontricks 2910532096 d3dx9

This installs all d3dx9 DLLs (versions 24 through 43) as native overrides in the game's Wine prefix. Ignore the wall of warnings, that is normal. After this, the game launched fine with no WINEDLLOVERRIDES needed.

If you are fighting with older DX9 games on the Deck, skip the launch option approach and go straight to Protontricks.