Comment 2 for bug 1852006

I had the same problem. I carefully pruned away all PPAs and the software installed from them. I did this by using software-properties-gtk and disabling all the repositories in 'Other Software' and then using aptitude to delete all packages in 'Obsolete or Local Packages'. However, this did not help.

While digging around in /var/log/dist-upgrade/apt.log (or was it main.log?), I saw that there were some packages that were identified as 'meta packages' and there were dependency resolution issues with some of these. These were:
xubuntu-desktop
ubuntu-unity-desktop
ubuntu-gnome-desktop
kubuntu-desktop
ubuntu-budgie-desktop
ubuntu-mate-desktop
lubuntu-desktop
Since I only need 1 of these to have a working system after the upgrade, I deleted them (except kubuntu-desktop and ubuntu-unity-desktop, I think), upgraded and then re-installed them.