Comment 3 for bug 1871176

I got this error after a few steps:

* After upgrading from eoan to focal and rebooting, I was dropped into the initramfs shell. Exiting from the shell, I see the error message "/dev/mapper/ubuntu--vg-root does not exist".

* After some searching online, I reboot using my previous kernel and reach the desktop.

* I open Synaptic and see that lvm2 was removed. When I try to install it, I get the error in this issue.

After some more searching online, I see https://askubuntu.com/questions/1049727/every-time-i-install-or-remove-a-package-i-get-lvm2-error/1085420 and try the suggested answer (purge lvm2 before reinstalling) - this worked.