Installed xfce, but it does not show up in the sddm greeter:
karl@erlangen:~> cat /etc/sysconfig/windowmanager
## Type: string
## Default:
## Path: Desktop
## Description: default mouse cursor theme
#
# Name of mouse cursor theme for X11. Possible themes can be found
# in /usr/share/icons/
#
X_MOUSE_CURSOR="DMZ"
## Path: Desktop/Window manager
## Description:
## Type: string(gnome,kde-plasma,kde,plasma5,lxde,**xfce**,twm,icewm)
## Default: kde-plasma
## Config: profiles,kde,susewm
#
# Here you can set the default window manager (kde, fvwm, ...)
# changes here require at least a re-login
DEFAULT_WM="kde-plasma"
## Type: yesno
## Default: yes
#
# install the SUSE extension for new users
# (theme and additional functions)
#
INSTALL_DESKTOP_EXTENSIONS="yes"
KDE_USE_IPV6="yes"
karl@erlangen:~>
And how did you install it?
In particular, did you also install lxde-common? This contains the session file that’s needed for it to be listed in a display manager.
karl@erlangen:~> cat /etc/sysconfig/windowmanager
That’s irrelevant.
It could only be used to set the default desktop session (and the mouse cursor), but sddm actually ignores this anyway and uses its own settings.
Have installed the following:
erlangen:~ # zypper install xfce4-session
Loading repository data...
Reading installed packages...
Resolving package dependencies...
The following application is going to be installed:
"Thunar File Manager"
The following 46 NEW packages are going to be installed:
gnome-icon-theme gnome-icon-theme-extras gnome-icon-theme-symbolic libgarcon-1-0 libgarcon-branding-openSUSE libgarcon-data libgarcon-lang libgsf-1-114
libkeybinder0 libthunarx-2-0 libtumbler-1-0 libunique-1_0-0 libxfce4panel-1_0-4 libxfce4panel-2_0-4 libxfce4ui-tools libxfsm-4_6-0 libxklavier16
openSUSE-xfce-icon-theme polkit-gnome thunar thunar-lang thunar-volman thunar-volman-branding-openSUSE thunar-volman-lang tumbler tumbler-lang xfce4-mixer
xfce4-mixer-lang xfce4-panel xfce4-panel-branding-openSUSE xfce4-panel-lang xfce4-panel-plugin-mixer xfce4-panel-plugin-power-manager xfce4-power-manager
xfce4-power-manager-branding-openSUSE xfce4-power-manager-lang xfce4-session xfce4-session-branding-openSUSE xfce4-session-lang xfce4-settings
xfce4-settings-branding-openSUSE xfce4-settings-lang xfce4-splash-branding-openSUSE xfdesktop xfdesktop-branding-openSUSE xfdesktop-lang
The following 20 recommended packages were automatically selected:
libgarcon-data libgarcon-lang libxfce4ui-tools thunar thunar-lang thunar-volman thunar-volman-lang tumbler tumbler-lang xfce4-mixer xfce4-mixer-lang
xfce4-panel xfce4-panel-lang xfce4-panel-plugin-mixer xfce4-panel-plugin-power-manager xfce4-power-manager-lang xfce4-session-lang xfce4-settings-lang
xfdesktop xfdesktop-lang
46 new packages to install.
Overall download size: 17.6 MiB. Already cached: 0 B. After the operation, additional 38.2 MiB will be used.
Continue? [y/n/? shows all options] (y):
That worked already. Then I added:
erlangen:~ # zypper install lxde-common
Loading repository data...
Reading installed packages...
Resolving package dependencies...
The following 27 NEW packages are going to be installed:
gtk2-engine-clearlooks gtk2-engine-crux gtk2-engine-glide gtk2-engine-hcengine gtk2-engine-industrial gtk2-engine-mist gtk2-engine-redmond95
gtk2-engine-thinice gtk2-engines gtk2-metatheme-gilouche gtk2-metatheme-industrial gtk2-theme-clearlooks gtk2-theme-crux gtk2-theme-industrial
gtk2-theme-mist gtk2-theme-redmond95 gtk2-theme-thinice libImlib2-1 libobrender32 libobt2 lxde-common lxde-common-branding-openSUSE obconf openbox
openbox-adwaita-ob-theme tango-icon-theme xkill
The following 8 recommended packages were automatically selected:
gtk2-engines gtk2-theme-clearlooks gtk2-theme-crux gtk2-theme-industrial gtk2-theme-mist gtk2-theme-redmond95 gtk2-theme-thinice obconf
27 new packages to install.
Overall download size: 14.8 MiB. Already cached: 0 B. After the operation, additional 24.9 MiB will be used.
Continue? [y/n/? shows all options] (y):
Now everything works. Thank you! 
Oops, you were actually asking about XFCE, so this wouldn’t have been necessary at all.
That’s needed for LXDE of course, not XFCE.
No idea how I could read LXDE here… :\
Now everything works. Thank you!
You were likely missing xfce-session then, which contains the session file for XFCE obviously.
Btw, it may be a better idea to use the corresponding patterns to not forget important packages.
See YaST->View->Patterns, or run something like “zypper in -t pattern xfce” (“zypper se -t pattern” will list all available patterns).
Encountered a problem with sound:
- graphical login A has sound with both kde-plasma
and xfce
- graphical login B has sound with kde-plasma
only
Any idea what is wrong with login B?
No. Maybe install/run pavucontrol and check the sound settings (volume and output).
But you should better open separate threads for unrelated problems…