For anyone searching on how to make the
save file work on linux. I will explain the process. I am doing this manually since I couldn't be bothered to get regedit to work using wine tbh.
I am using Lutris with Wine. Make sure to set the Wine prefix. That's just a directory where it will save everything. something like "~/Games/SomethingUnlimited"
I am using cachyOs so for the wine version I am using proton-cachyos. for the win version in runner options. This shouldn't matter much as long as your are using proton. and inside the win prefix folder you have user.reg That's your target.
here is the save file.
You will open the 2.4.8.reg file using any editor of choice. I am using vscode.
You shall see this stuff.
Select everything from "screen manager to the bottom of the file.
and you will open the user.reg that is found in the root of the wine prefix folder.
You can see where this is going here. replace everything you see with what you copied to user.reg from "Screenmanager" to just above "UnityGraphicsQuality" as seen in the image.
Basically you are replacing the variables with the ones in the save file. And you are done. The save file works on linux under lutris proton.