That finally solved it for me, thank you @Eberhard and @all for looking into this and sharing your insights!
A few notes:
* in addition, I manually deleted file /etc/X11/Xsession.d/20dbus_xdg-runtime which comes with package dbus-user-session (and is actually the only file of the package) but was not removed on uninstall (Idk whether this step is always neccessary)
* logout/login was not sufficient to see this solved. Full reboot was required.
That finally solved it for me, thank you @Eberhard and @all for looking into this and sharing your insights!
A few notes:
* in addition, I manually deleted file /etc/X11/ Xsession. d/20dbus_ xdg-runtime which comes with package dbus-user-session (and is actually the only file of the package) but was not removed on uninstall (Idk whether this step is always neccessary)
* logout/login was not sufficient to see this solved. Full reboot was required.