I encountered a bug when installing Qubes 4.1-rc2.
During installation, I entered the username “sync”.
The installer accepted the username and after formatting the disk, the system rebooted. When I attempted to login to complete the installation, the system rejected the username & password.
I attempted the same install with the same username two more times with the same results. When I eventually changed the username during setup, Qubes installed properly.
The bug is identical to the 4.0 bug described here:
The only difference is the username itself. It’s not clear if the “qubes” username bug still exists, was fixed at a deeper level or was just patched to allow the username “qubes”.
Perhaps the fact that “sync” also causes the same behavior might help devs identify the underlying cause of the original problem.