I tested additional Proton versions and found a change in the UI rendering behavior: Proton 3–4: game does not run Proton 5–8: game runs, but UI is heavily corrupted with rainbow/glitchy artifacts Proton 9+: game runs, b...
The problem is not limited to the main menu. UI elements throughout the game are visually broken, while their input areas still appear to function. I was able to navigate into the game by clicking UI elements blindly, an...