Guide (works for games and normal Windows programs)

Source: Linux: How to play Diablo II: Resurrected (Open Beta) with Steam (Proton)

Install Steam

1. Enable the multilib repository.
2. Install steam with yay -S steam
3. Start steam minimized: add -silent flag to 'Exec' line in ~/.config/autostart/steam.desktop
4. Install bchunk to convert BIN/CUE files to ISO (which can be mounted natively in the KDE/GNOME file explorers.)

Install Windows game/program:

1. Download the install .EXE & install files, OR mount the install ISO.
2. In steam, go to games -> add non-Steam game to library
3. Browse to install.exe file for game and complete adding to library
4. Open the Steam properties for the game, change name if desired, force a particular Proton version if the default does not work.
5. Launch the installer via Steam, follow the normal install procedure for the program, leave the install paths at defaults.

• The Game is now installed at the location ~/.local/share/Steam/steamapps/compatdata/[wineprefix]/pfx/drivec/ (below this folder is a fake Windows directory structure, the program is installed in here). Steam does not tell you which wineprifix number goes to which game, so you have to search inside each one to find the correct directory/excecuteable.

6. (optional) If there are additional expansions/mods/feature packs to add onto the original install, open the game properties in steam again and change the EXE path to the additional installer(s), one at a time, and run the game again. This will install the extra software in the same directories as the original installer.

7. After the install is complete, change the game properties to point to the game launcher EXE, which will be in ~/.local/share/Steam/steamapps/compatdata/[wineprefix]/pfx/drivec/[Windows/path/to/]launcher.exe

8. The game can now be launched from Steam.