I think stage 1 has failed (whonix-ws and debian_2nd templates) during R4.1 → R4.2 upgrade. Later I did cmd line upgrade on dom0 sudo qubes-dom0-update and it has asked to reboot to continue the upgrade.
After the reboot, qubes doesn’t boot up anymore. Getting stuck at the message “[ 4.602791] dracut-cmdline[286]: Warning: USB in dom0 is not restricted. Consider rd.qubes.hide_all_usb or usbcore.authorized default=0.”
After going to “advanced” menu, I managed to view boot messages.
As per screenshot, it just sits there.