Well if the update was happening when you rebooted the system, then chances are you have a mix of a 9.2 and 9.3 system. You’ll have to boot into rescue mode with network connection and chroot into the installation, to then attempt continuing the upgrade process. Then exit chroot and reboot.
You failed to mention in your initial post that you were upgrading at the time you forced a reboot.
It takes a while sometimes to think… we won’t mention my search for the Linux boot menu. “But the is at the start of every boot” unless you have a weird graphics cards set up where it is displayed on a different card.
I’ll have a read up on this before I try anything.