I installed the windows version from steam. The game does not run under proton 8.0-5, but does with the current versions of experimental and Proton-GE from the AUR.
I did not need to set windows version to XP, or do any other kind of extra fiddling. So all you should need is to set the no DRM launch option in heroic to allow the Epic version to run.
If you haven’t installed that Proton-GE package from the AUR, I suggest doing so. It’s been the only “custom” proton version I’ve needed for ages, it gets updated when a new version comes out and makes itself available for selection in both Steam and Heroic, so it’s a very set and forget way to use the GE versions of Proton.