Repairing severe apt install problem ubuntu

1. Lubuntu is really nice, processes look fluent,  besides it is really stable and robust, though it doesn't let any error pass. 
2. Off course it uses lightdm.
3. Actually serious errors can be corrected but manually.
4. I performed the procedure of upgrading from 18.04 into 19.04, many things have changed, but many errrors did appear meanwhile.
5. Amongst the minor errors we cite the disappearance of the icons, I retrieved them through switching from the gdm3 into lightdm, and when I change some gnome into Lubuntu.
6. As for the serious errors, I think the corruption of the apt command is the toughest one, I failed to install anything any more, any operation of installation ended with an indication that there a non satisfied interdependance resulting from inconsistencies within the python3 in the distro core; this came from the upgradin operation. Some time a red message about a sever dpkg error appears.
7. I have tried any proposed combination of commands on the net like apt clean, remove, autoremove, upgrade, fullupgrade, dist-upgrade, update, --fix-missing, purge, repairing dpkg even from the grub menu, all failed, the solution has been to empty /var/lib/dpkg/info/ , after that we can proceed to apt-get install upgrade and update and install missing packahes like gdm3.

Good link about the matter : http://doc.ubuntu-fr.org/probleme_apt