I have the exact same problem that is probably linked to the apt-get autoremove I did on both the gateway and the workstation.
I did not do any whonix update appart from the usual sudo apt-get update && sudo apt-get dist-upgrade.
Next reboot I was locked out.
Following your advice I managed to open a virtual console and could log in with my current login and pass.
sudo apt-get update && sudo apt-get dist-upgrade do not find anything missing yet something definitely is.
I have very important information on the workstation that I cannot afford to loose, i'm totally freaked out right now.
When you say :
Then try to fix the broken dependencies.
sudo apt-get update
sudo apt-get install non-qubes-whonix-gateway
If I do that with the correct command for the workstation, will it delete my data ??? I did use the export appliance like you recommended.
It seems all the data is untouched and it is probably trivial to get it back for a power user but I'm totally lost right now.
I followed your advice on the gateway and it works like before. I have no personal data on it so I have no idea if anything was deleted from it or not. I would guess not as login and pass did not change and keyboard layout is back to what it was.
I will wait for confirmation that it is safe for my data to do the same thing on the workstation.