GloriousEggroll has released a new custom build of their Proton fork.

Proton-6.5-GE-2

General Proton fixes:

-Added mouse stutter fix from proton experimental
-Fullscreen hack is back! Works with MK11 finally!

Game fixes:

-Fixed RDR2 Online mode, works now
-Fixed GTA V forcing players into solo online sessions and making them unable to join events
-Fixed Sea of Thieves crash on loading after creating a new lobby
-Fixed issue with games exiting and leaving steam in 'running' mode
-Added launcher workaround for Evil Genius 2

MFPlat fixes:

-Fixed MK11 random mid-game/mid-cutscene mfplat crashes (hopefully)

Known issues:

-MK11 will crash in story mode on chapter select if you do not select a level before one of the video clip animations completes
-Catherine Classic still doesn't work
-Darksiders Warmastered Edition still doesn't work
-Grandia/Grandia II HD Remaster still crash on opening.

Download Proton 6.5-GE-2 from GitHub
Installation Instructions