Comment 2 for bug 1694513

The error in your log is:

debconf: unable to initialize frontend: Passthrough
debconf: (Cannot connect to /tmp/aptdaemon-klnuxv1j/debconf.socket: Connection refused at (eval 18) line 3.)
debconf: falling back to frontend: Noninteractive
Running in non-interactive mode, doing nothing.
dpkg: error processing package shim-signed (--configure):
 subprocess installed post-installation script returned error exit status 1

I see that this happens when you are installing some dkms packages (bbswitch-dkms, and nvidia). How have you selected these for installation? Did you use the 'Software & Updates' Additional Drivers GUI?