I have checked C:\Windows\Panther\setuperr.log and it is empty, but C:\Windows\Panther\UnattendGC\setuperr.log has this line in it:
2023-09-01 11:50:02, Error [CloudExperienceHostBroker.exe] Disabling default account failed [hr=0xD00000E5]
I believe CloudExperienceHostBroker.exe is what runs the OOBE setup as the defaultuser on first boot of a generalised image.
The bottom of the C:\Windows\Panther\UnattendGC\setupact.log, has this in it where you can see this error too, but also the delay whilst I then manually reboot the machine to get it to finish (I think the hours are skewed due to initial timezone being wrong until I reboot):
2023-09-01 11:50:02, Info [taskhostw.exe] OOBE Monitor event received: 999
2023-09-01 11:50:02, Info [CloudExperienceHostBroker.exe] Clearing Auto-logon values per request
2023-09-01 11:50:02, Info [CloudExperienceHostBroker.exe] Transferring unattend.xml autologon values
2023-09-01 11:50:02, Error [CloudExperienceHostBroker.exe] Disabling default account failed [hr=0xD00000E5]
2023-09-01 14:03:15, Info [svchost.exe] Enter WinReIsWimBootEnabled
2023-09-01 14:03:15, Info [svchost.exe] Parameters: pszWinDir: NULL
2023-09-01 14:03:15, Info [svchost.exe] Exit WinReIsWimBootEnabled returns 0 with last error: 0x2
So, is it this that is causing the OOBE to hang and not reboot like it should, perhaps?