Like an idiot I always upgrade stuff. Can’t help it. I know better. Really. I do.
I ran the install and got an error that apt’s post install script failed. Then it kept going for some time. And then it decided it had failed and my system was in an unstable state. Have a nice day.
I could still boot to the old kernel (the new kernel worked but the system was too trashed to rebuild the Nvidia drivers).
Turns out in /var/lib/dpkg/info/apt.postinst there is a function called:
What’s more is down a ways in the script it calls this line and that is what makes it fail. Three hash signs later and the system is happily configuring away!
Hope that is useful info for you.