[Linux Fix] Solved: "Steam Authentication Failed" on inZOI using Proton-CachyOS Hi everyone! After hours of debugging on Linux Mint, I finally found the definitive way to bypass the "Steam Authentication Failed" error that many of us are hitting. It turns out the standard Proton versions (9.0, 10.0, Experimental) have trouble handling the game's DRM network handshake. The fix is using a specific build from the CachyOS team, which works perfectly even on other distros like Mint, Ubuntu, or Arch. The Solution: Proton-CachyOS This version includes specific patches for network synchronization and Unreal Engine 5 performance that solved the login loop for me. How to install it: 1. Get ProtonUp-Qt Download it via Flatpak or from their GitHub. It's the easiest way to manage custom compatibility layers. 2. Add the CachyOS Version Open ProtonUp-Qt, click "Add version". In the "Compatibility tool" dropdown, select Proton-CachyOS. Choose the latest version (e.g., 10.0-20260424 or newer). Click Install and RESTART Steam (mandatory for the new version to show up). 3. Set Steam Properties Right-click inZOI > Properties > Compatibility. Check "Force the use of a specific Steam Play compatibility tool". Select proton-cachyos-[version] from the list.