Attempted to use several different proton versions, including GE; Unreal Engine here seems to use(leak?) over 16 gigabytes of memory and will crash your system without a safety net like earlyoom. Further reading leads me to believe this was a problem several years ago with certain DX11 games, but attempting to play with PROTON_USE_WINED3D11=1 %command% slows the game's main menu to a crawl. Presumably an artifact of it being an unstable demo at time of writing, or a problem with this specific NVidia driver. It may be possible to get around with some tinkering.