Since a few weeks I can not start yast2 from the menu.

The command line behind the menu entry is:
> /usr/bin/xdg-su -c /sbin/yast2

If I enter this command in a terminal I get this output:
> No protocol specified
> lxqt-sudo: Stripping child environment except for: DISPLAY, LANG, LANGUAGE, LC_ADDRESS, LC_ALL, LC_COLLATE, LC_CTYPE, LC_IDENTIFICATION, LC_MEASUREMENT, LC_MESSAGES, LC_MONETARY, LC_NAME, LC_NUMERIC, LC_PAPER, LC_TELEPHONE, LC_TIME, PATH, QT_PLATFORM_PLUGIN, QT_QPA_PLATFORMTHEME, WAYLAND_DISPLAY, XAUTHORITY
> 
> No protocol specified
> No protocol specified
> qt.qpa.screen: QXcbConnection: Could not connect to display :0
> Could not connect to any X display.
> qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
> qt.qpa.plugin: Could not find the Qt platform plugin "wayland" in ""
> This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.
> 
> Available platform plugins are: eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, xcb.
> 
> /sbin/yast2: Zeile 455:  8361 Abgebrochen             (Speicherabzug geschrieben) $y2ccbin $Y2UI_ARGS "$@"


If I do first "su -" and call then "yast2" everything is fine.