Public bug reported: When switching the displaymanager from sddm to lightdm, login fails due to misconfigured lightdm configuration file.
$ cat /usr/share/lightdm/lightdm.conf.d/40-kde-plasma-kf5.conf [SeatDefaults] user-session=kde-plasma-kf5 $ls /usr/share/xsessions/* /usr/share/xsessions/plasma.desktop ##### Changing /usr/share/lightdm/lightdm.conf.d/40-kde-plasma-kf5.conf to $ cat /usr/share/lightdm/lightdm.conf.d/40-kde-plasma-kf5.conf [SeatDefaults] user-session=plasma or renaming /usr/share/xsessions/plasma.desktop to /usr/share/xsessions /kde-plasma-kf5.desktop solves the issue. ##### $ lsb_release -rd Description: Ubuntu 16.04.1 LTS Release: 16.04 $ apt-cache policy plasma-workspace plasma-workspace: Installed: 4:5.5.5.2-0ubuntu1 Candidate: 4:5.5.5.2-0ubuntu1 Version table: *** 4:5.5.5.2-0ubuntu1 500 500 http://de.archive.ubuntu.com/ubuntu xenial/universe amd64 Packages 100 /var/lib/dpkg/status ##### ** Affects: plasma-workspace (Ubuntu) Importance: Undecided Status: New ** Tags: kde lightdm plasma sddm -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1629543 Title: KDE does not start when using lightdm To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/plasma-workspace/+bug/1629543/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs