Bug#1042762: sddm: SDDM freezes after switching to a user from KDE Plasma and logging out of the second session

[Chandra Sekar <chandru.in@gmail.com>]

Package: sddm
Version: 0.19.0-5
Severity: important
X-Debbugs-Cc: chandru.in@gmail.com

Dear Maintainer,

Steps to Reproduce

1. Create 2 users.
1. Log into KDE plasma as user1.
1. Use Plasma's "Switch User" function to switch to user2.
2. Log out from user2's session.

Expected Behaviour

A login screen must be presented, allowing the user to log into any of
the accounts available in the machine.

Actual Behaviour

The login screen is frozen. Switching to user1's session, using
Ctrl+Alt+F1, and selecting "Switch User" again creates a new login
screen in a new TTY8. The old one remains stuck in TTY7.

This appears to be fixed in 0.20.0-1, which is available in unstable.
Since this issue renders the switch users functionality nearly unusable,
can you please backport the fix or make 0.20.0 available in bookworm?

-- System Information:
Debian Release: 12.1
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable-security'), (500, 'stable')
Architecture: amd64 (x86_64)

Kernel: Linux 6.1.0-10-amd64 (SMP w/12 CPU threads; PREEMPT)
Locale: LANG=en_IN, LC_CTYPE=en_IN (charmap=UTF-8), LANGUAGE=en_IN:en
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages sddm depends on:
ii  adduser                 3.134
ii  debconf [debconf-2.0]   1.5.82
ii  libc6                   2.36-9+deb12u1
ii  libgcc-s1               12.2.0-14
ii  libpam0g                1.5.2-6
ii  libqt5core5a            5.15.8+dfsg-11
ii  libqt5dbus5             5.15.8+dfsg-11
ii  libqt5gui5              5.15.8+dfsg-11
ii  libqt5network5          5.15.8+dfsg-11
ii  libqt5qml5              5.15.8+dfsg-3
ii  libqt5quick5            5.15.8+dfsg-3
ii  libstdc++6              12.2.0-14
ii  libsystemd0             252.12-1~deb12u1
ii  libxcb-xkb1             1.15-1
ii  libxcb1                 1.15-1
ii  qml-module-qtquick2     5.15.8+dfsg-3
ii  x11-common              1:7.7+23
ii  xauth                   1:1.1.2-1
ii  xserver-xorg [xserver]  1:7.7+23

Versions of packages sddm recommends:
ii  libpam-systemd                         252.12-1~deb12u1
ii  sddm-theme-breeze [sddm-theme]         4:5.27.5-2
ii  sddm-theme-debian-breeze [sddm-theme]  4:5.27.5-2

Versions of packages sddm suggests:
ii  libpam-kwallet5           5.27.5-2
pn  qtvirtualkeyboard-plugin  <none>

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