Sometimes, seemingly randomly, you can get an EAC error during the VRChat startup/login screen. It looks like a message box, with the title "Anti-cheat Error", no actual message text, and a single button labeled "Quit".
It is likely caused by a race condition. Closing unnecessary apps or otherwise **lowering your CPU usage** before starting VRChat seems to make the EAC error happen significantly less often. It is safe to crank the CPU usage back up after the home world has loaded.
In other games with EAC, getting past the EAC splash screen had required glibc to be built with a specific flag to work.<sup>[1],[2]</sup> (`--hash-style=both`)