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Yes thats exactly what I did. At first I tried to run it with default proton but that didn’t work so after it failed I switched to proton experimental it worked no problems. I added the folder with the exe and other files to my documents folder and added the exe within the folder to steam as a non steam game

Yes it works perfectly for me, I’m on the stable steamos branch and added the exe directly to steam 

the game works on SD if you add it to steam as a non steam game and run it with proton experimental