Muss man also selbst dafür sorgen, das Fremdquellen hinzugefügt werden, wie schon immer™.
alles andere hätte mich auch schwer gewundert
frieder@mate:~$ grep -P '^ *[^# ]' /etc/apt/sources.list /etc/apt/sources.list.d/*.list /etc/apt/sources.list:deb http://de.archive.ubuntu.com/ubuntu/ xenial main restricted /etc/apt/sources.list:deb-src http://de.archive.ubuntu.com/ubuntu/ xenial main restricted /etc/apt/sources.list:deb http://de.archive.ubuntu.com/ubuntu/ xenial-updates main restricted /etc/apt/sources.list:deb-src http://de.archive.ubuntu.com/ubuntu/ xenial-updates main restricted /etc/apt/sources.list:deb http://de.archive.ubuntu.com/ubuntu/ xenial universe /etc/apt/sources.list:deb-src http://de.archive.ubuntu.com/ubuntu/ xenial universe /etc/apt/sources.list:deb http://de.archive.ubuntu.com/ubuntu/ xenial-updates universe /etc/apt/sources.list:deb-src http://de.archive.ubuntu.com/ubuntu/ xenial-updates universe /etc/apt/sources.list:deb http://de.archive.ubuntu.com/ubuntu/ xenial multiverse /etc/apt/sources.list:deb-src http://de.archive.ubuntu.com/ubuntu/ xenial multiverse /etc/apt/sources.list:deb http://de.archive.ubuntu.com/ubuntu/ xenial-updates multiverse /etc/apt/sources.list:deb-src http://de.archive.ubuntu.com/ubuntu/ xenial-updates multiverse /etc/apt/sources.list:deb http://de.archive.ubuntu.com/ubuntu/ xenial-backports main restricted universe multiverse /etc/apt/sources.list:deb-src http://de.archive.ubuntu.com/ubuntu/ xenial-backports main restricted universe multiverse /etc/apt/sources.list:deb http://security.ubuntu.com/ubuntu xenial-security main restricted /etc/apt/sources.list:deb-src http://security.ubuntu.com/ubuntu xenial-security main restricted /etc/apt/sources.list:deb http://security.ubuntu.com/ubuntu xenial-security universe /etc/apt/sources.list:deb-src http://security.ubuntu.com/ubuntu xenial-security universe /etc/apt/sources.list:deb http://security.ubuntu.com/ubuntu xenial-security multiverse /etc/apt/sources.list:deb-src http://security.ubuntu.com/ubuntu xenial-security multiverse grep: /etc/apt/sources.list.d/*.list: Datei oder Verzeichnis nicht gefunden frieder@mate:~$
/etc/apt/sources.list.d/ ist komplett leer und auch sonst ist nirgendwo ein PPA zu sehen.