I've had trouble with switch user for the last 2 years at least. For a long time the option was gone because of some deep regression. Now that it's back, it doesn't work. Activating 'Switch user' gives a black screen (no mouse).
From the syslog:
sddm: Initializing...
sddm: Starting...
sddm: Logind interface found
sddm: Adding new display on vt 1 ...
sddm: Loading theme configuration from ""
sddm: Display server starting...
sddm: Adding cookie to "/var/run/sddm/{d006b35c-9f22-4bfa-84b0-8ae8685ded1a}"
sddm: Running: /usr/bin/X -nolisten tcp -auth /var/run/sddm/{d006b35c-9f22-4bfa-84b0-8ae8685ded1a} -background none -noreset -displayfd 17 -seat seat0 vt1
sddm: Setting default cursor
sddm: Running display setup script "/usr/share/sddm/scripts/Xsetup"
sddm: Display server started.
sddm: Socket server starting...
sddm: Socket server started.
sddm: Loading theme configuration from "/usr/share/sddm/themes/ubuntu-theme/theme.conf"
sddm: Greeter starting...
sddm-helper Starting...
sddm-helper Authenticating...
sddm-helper returning.
systemd: Started Session 1 of user sddm.
sddm: Greeter session started successfully
sddm-greeter: High-DPI autoscaling not Enabled
sddm-greeter: Reading from "/usr/share/xsessions/plasma.desktop"
sddm-greeter: Reading from "/usr/share/xsessions/ubuntu-xorg.desktop"
sddm-greeter: Reading from "/usr/share/xsessions/ubuntu.desktop"
sddm-greeter: Reading from "/usr/share/wayland-sessions/plasmawayland.desktop"
sddm-greeter: Reading from "/usr/share/wayland-sessions/ubuntu.desktop"
sddm-greeter: Loading theme configuration from "/usr/share/sddm/themes/ubuntu-theme/theme.conf"
sddm-greeter: Connected to the daemon.
sddm: Message received from greeter: Connect
sddm-greeter: Loading file:///usr/share/sddm/themes/ubuntu-theme/Main.qml...
sddm-greeter: QObject: Cannot create children for a parent that is in a different thread.#012(Parent is QGuiApplication(0x7fff6abea430), parent's thread is QThread(0x56178f8970a0), current thread is QThread(0x56178f985630)
sddm-greeter
sddm-greeter: QObject::installEventFilter(): Cannot filter events for objects in a different thread.
dbus-daemon Activating via systemd: service name='org.freedesktop.UPower' unit='upower.service' requested by ':1.45' (uid=115 pid=2435 comm="/usr/bin/sddm-greeter --socket /tmp/sddm-:0-yjuzno" label="unconfined")
sddm-greeter: <input>:406:376: Could not add child element to parent element because the types are incorrect.
sddm-greeter: <input>:407:130: Could not add child element to parent element because the types are incorrect.
sddm-greeter: <input>:408:130: Could not add child element to parent element because the types are incorrect.
sddm-greeter: <input>:408:393: Could not add child element to parent element because the types are incorrect.
sddm-greeter: <input>:409:130: Could not add child element to parent element because the types are incorrect.
sddm-greeter: <input>:410:129: Could not add child element to parent element because the types are incorrect.
sddm-greeter: <input>:411:129: Could not add child element to parent element because the types are incorrect.
sddm-greeter: <input>:412:129: Could not add child element to parent element because the types are incorrect.
sddm-greeter: <input>:413:129: Could not add child element to parent element because the types are incorrect.
sddm-greeter: <input>:413:379: Could not add child element to parent element because the types are incorrect.
sddm-greeter: <input>:413:631: Could not add child element to parent element because the types are incorrect.
sddm-greeter: fromIccProfile: invalid tag offset alignment
sddm-greeter: Adding view for "LVDS-1-1" QRect(0,0 1920x1080)
sddm-greeter: Message received from daemon: Capabilities
sddm-greeter: Message received from daemon: HostName
In the syslog I also have a lot of:
sddm-greeter: file:///usr/share/sddm/themes/ubuntu-theme/components/ActionButton.qml:62: TypeError: Cannot read property 'longDuration' of null
sddm-greeter: file:///usr/share/sddm/themes/ubuntu-theme/components/ActionButton.qml:78: TypeError: Cannot read property 'shortDuration' of null
I have tried changing theme, but no change.
