For those who have a non-stream version of FFXIV. First download the trial version of FFXIV of Steam in game-mode. Run it once and close the game. Open in desktop mode. Using Discovery (bottom left shopping bag icon) search for ProtonUp-QT. Install and open it up. Click on add version and install the latest GE-Proton which in my case was 7.10. Navigate to folder /home/deck/.local/share/Steam/steamapps/compatdata/312060/pfx/drive_c/users/steamuser/My Documents/My Games/FINAL FANTASY XIV - A Realm Reborn and open up FFXIV-Boot.cfg in a text editor. Note 312060 is the FFXIV Demo trial which I am using to play FFXIV on as I have the Square Enix version. Change the values for Browser and BrowserType to 1 and save. Go back to Game Mode. go to properties of the FFXIV game and change the launch option to be NOSTEAM %command% and save. Now open up the game and you should be able to see the launcher for you to type in your user name and password and play the game.