if you have an updated protontricks install, you should just be able to run "protontricks" in terminal, and select the game within the GUI. Then click "Select the default wine prefix" then select "run winecfg". Then at the bottom of this main menu you should see "Windows Version (Windows 10). Change it to windows 7 and save it.
If for some reason you do not see ephinea in that list, it probably means protontricks isnt great at detecting non steam games. In which case you'd probably want to do the "protontricks <GAME_ID> winecfg". But how do you find the game id you may ask? Well if you installed it via steam its probably got some sort of id within the steam compat folder, or at least i hope it does. 2 options to potentially find it, right click the game in steam and try browse local files. (but the problem with this is steam puts the actual game files in a directory different than the wine/proton build. you want to be looking at compatdata usually, not steamapps/common). If that doesn't work try something more manual, like comparing the "last modified date" to find it yourself and narrow down what is the actual location of the wine prefix of PSO.
and yes you'd want to replace <GAMEID> with the actual gameid. it should be like a 12 character long string/word. that was just a placeholder.
if all the above doesnt work, you will need to do something a bit more tech savvy and harder, which is figure out how to do this ". WINEPREFIX=PATH/TO/MY/PREFIX winecfg -v win7" or "export WINEPREFIX=PATH/TO/MY/PREFIX winecfg" to run the gui. but again it could be different with proton.
