The Haunted began as an Unreal Tournament 3 total conversion which one the "Make Something Unreal" competition. The developers used their earnings to develop a full professional release: Hell's Reach
Improving on the original mod you can play co-op with 3 friends online and slay all kinds of new demons in the original maps or a few new maps. New features and weapon upgrades available as well. And to top-it-off... a final boss ending!
I originally posted a guide for The Haunted as an Unreal Tournament 3 guide, but later posted Hell's Reach in PlayOnLinux. The game ran fine and Wine handled Unreal engine without any issues. The only problem was installing Windows Steam and configuring everything in PlayOnLinux. Today Proton makes it simple and easy. Download, set compatibility with Proton and play. Nuff Said!
Mint 19.3 64-bit
GeForce GTX 1060