Bug#897338: sddm: Cannot launch SDDM at boot time and from console

[Alexander Kernozhitsky <sh200105@mail.ru>]

Package: sddm
Version: 0.17.0-1
Severity: grave
Justification: renders package unusable

Dear Maintainer,

I tried to do a fresh install of Debian Testing with KDE. After installing it, SDDM did not launch. Launching it manually with "sudo systemctl start sddm" did not have effect also.

"systemctl status sddm" shows the following:

● sddm.service - Simple Desktop Display Manager
   Loaded: loaded (/lib/systemd/system/sddm.service; indirect; vendor preset: enabled)
   Active: active (running) since Tue 2018-05-01 16:56:33 +03; 12min ago
     Docs: man:sddm(1)
           man:sddm.conf(5)
  Process: 412 ExecStartPre=/bin/sh -c [ "$(cat /etc/X11/default-display-manager 2>/dev/
 Main PID: 421 (sddm)
    Tasks: 2 (limit: 1156)
   Memory: 11.7M
   CGroup: /system.slice/sddm.service
           └─421 /usr/bin/sddm

Though I don't see the login screen, tty7 is blank.

I tried to rebuild and install sddm from Ubuntu Bionic (where it works), but met the same problem. Installing sddm 0.14.0-4 from stable did solve the problem.

-- System Information:
Debian Release: buster/sid
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: amd64 (x86_64)

Kernel: Linux 4.15.0-3-amd64 (SMP w/2 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE=en_US:en (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages sddm depends on:
ii  adduser                 3.117
ii  debconf [debconf-2.0]   1.5.66
ii  libc6                   2.27-3
ii  libgcc1                 1:8-20180425-1
ii  libpam0g                1.1.8-3.7
ii  libqt5core5a            5.10.1+dfsg-5
ii  libqt5dbus5             5.10.1+dfsg-5
ii  libqt5gui5              5.10.1+dfsg-5
ii  libqt5network5          5.10.1+dfsg-5
ii  libqt5qml5              5.10.1-4
ii  libqt5quick5            5.10.1-4
ii  libstdc++6              8-20180425-1
ii  libsystemd0             238-4
ii  libxcb-xkb1             1.13-1
ii  libxcb1                 1.13-1
ii  qml-module-qtquick2     5.10.1-4
ii  x11-common              1:7.7+19
ii  xserver-xorg [xserver]  1:7.7+19

Versions of packages sddm recommends:
ii  libpam-systemd                       238-4
ii  sddm-theme-debian-maui [sddm-theme]  0.17.0-1

Versions of packages sddm suggests:
ii  libpam-kwallet5           5.12.1-1
pn  qtvirtualkeyboard-plugin  <none>

-- debconf information:
* shared/default-x-display-manager: sddm
  sddm/daemon_name: /usr/bin/sddm