UPDATE Still trying to repair the upgrade of ubuntu 20.04.
the command apt-get upgrade did give the hint:
mailman3-web (0+20180916-10) wird eingerichtet ... dbconfig-common: writing config to /etc/dbconfig-common/mailman3-web.conf dbconfig-common: flushing administrative password CommandError: Offline compression is disabled. Set COMPRESS_OFFLINE or use the --force to override. dpkg: Fehler beim Bearbeiten des Paketes mailman3-web (--configure): »installiertes mailman3-web-Skript des Paketes post-installation«-Unterprozess gab den Fehlerwert 1 zurück dpkg: Abhängigkeitsprobleme verhindern Konfiguration von mailman3-full: mailman3-full hängt ab von mailman3-web; aber: Paket mailman3-web ist noch nicht konfiguriert.
Therefor i set in mailman3-conf.py: COMPRESS_OFFLINE=TRUE
Now the system is at the point: Compressing... done Compressed 2 block(s) from 63 template(s) for 1 context(s). Rebuilding indexes database for python3 version. This may take some time.
There are almost 100 list included in this postgresql-database, therefor i absolutely guess it will take some time.
Maybe somebody of u know what happening and am i on the right way?