Machine won't finish booting after update

[Fulko Hew]

I decided to log out and log back in to my X11 based KDE session just now,
and I saw that 'Discover' was telling me I had updates available.
So I said 'go ahead'.
Eventually, it said I needed to reboot, so I did.
After 4 (or 5) reboots that the machine drove itself through,
the last reboot failed to start up to a GUI session.

As a matter of fact, it dropped me down and told me it needed to enter an
emergency boot
and asked for my root password.
The message also told me to look at 'journalctl -xb'
After a few thousand lines of info, I saw nothing of significance
other than it hadn't finished.

The other suggestion was 'systemctl default'.
That resulted in the following:

Failed to mount /boot/efi
Dependency failed for Local File System
Dependency failed for Mark the need to relabel after reboot
Failed to mount RPC File System
Dependency failed for rpc-pipefs.target
Dependency failed for RPC security service for NFS client and server
Failed to start Load Kernel Modules
Failed to mount Arbitrary Executable File Formats File System
Failed to mount Arbitrary Executable File Formats File System
Failed to mount Arbitrary Executable File Formats File System
Failed to mount Arbitrary Executable File Formats File System
Failed to mount Arbitrary Executable File Formats File System
Failed to start Set Up Additional Binary Formats

... and then nothing.  I had to cold start
and that brings me back to the same issues.
Trying to reboot a previous kernel doesn't even result in any boot messages.

I now have a 'non-working' machine.
Suggestions are welcome (and needed)!

TIA
Fulko