I remember I originally got this on a disk in a box of Kellogg's Nutri-Grain. Got it on Steam recently and it didn't work out-the-box with proton; but the community expansion (virtually an entirely rebuilt game) works perfectly.

To get the community expansion to work simply:

• download the Star Wars Galactic Battlegrounds Expanding Fronts .zip
• unzip the content into the head folder which, for me was: ~/.steam/debian-installation/steamapps/common/'STAR WARS - Galactic Battlegrounds Saga'
• drag and drop the contents of the newly generated GAME folder into the folder named Game and accept all merges and replacements.
• in the Game folder, delete the current player.exe and rename the file battlegrounds_x2.exe to player.exe
• on launching the game in steam or however you acquired the original game, you will get a configuration screen, mess with the resolution in the configuration screen, it took me three changes to get mine perfect.