

The game complains about an "actions.json" at the start, which would be used for input mapping. You don't actually need this file, but you can copy it from other games to the EVERSLAUGHT steam directory. In my proton build page you'll be able to download an actions.json file for convenience.
When exiting the game, it doesn't exit properly. You have to focus the steam window and click on the green "EXIT" button for it to completely exit.
Regular proton at the time of this report does not work with the game, so based on instruction from the bug report I have made my own proton build capable of running it, which you can check here: https://github.com/Patola/wine/releases/tag/6.3-everslaught -- all the instructions are there. Do not download and run random stuff from the internet: first verify my profile and my history of contributions, both here on protondb and on github, for assurance that I have been doing that for a long time already and will have no malicious intent with my build.

Game currently doesn't work apparently due to an in unimplemented call.
Opened bug report at Valve at https://github.com/ValveSoftware/Proton/issues/5037 and explained the problems (action.json dialogue and XR_KHR_win32_convert_performance_counter_time function uninplemented). These are actually small issues and from previous bug reports I think Valve or voluntaries will be quick to fix that, maybe 2 weeks to one month. As soon as I notice it has been resolved, I will post a new protondb report with the positive results.

Starts, but not in VR -- appears on the screen and it's unresponsive to input.
At first the steam overlay complains about the game lacking an actions.json file which I then borrowed from other game (Shadow Legends VR) and it stopped complaining. It didn't make the game work, though. Bug report here: https://github.com/ValveSoftware/Proton/issues/5037