Error upgrading from Ubuntu 18.04 to 20.04

[Paul Smith]

This past weekend I decided to upgrade my system from 18.04 LTS to
20.04 LTS (yes, I know all about it not being officially offered until
18.04.1).  I had upgraded my desktop from 19.10 to 20.04 with no
problems.

However, for the very first time in as long as I can remember I had a
problem during the upgrade... 

If you're interested see:
https://bugs.launchpad.net/ubuntu/+source/dpkg/+bug/1883980

The thing is that my system is MOSTLY OK, but as I use it I can see
there are problems.  For example I discovered that the adwaita-icon-
theme-full package was missing; installing that helped a lot.  But, now
I'm wondering what other packages should have been installed that
weren't.

Running dpkg --configure -a doesn't seem to do anything.  Also running
apt dist-upgrade doesn't seem to want to install much of anything
interesting.

Does anyone know where I can find a list of packages that are installed
on a basic Ubuntu 20.04 LTS workstation system, that I can compare to
what I have installed and look for missing things?  Is such a thing
published somewhere or do I have to install in a VM or somesuch?