Имеем KDE на 9ой платформе, и x2goserver.
При подключении к машине, если указано разрешение > 1280x768 (влоть до Полноэкранного), видим только черный экран. В хомяке пользователя создается лог типа .xsession-x2go-citto-osa-05l.adm72.local-errors
в котором, интересны последние строчки

[50061:50061:0506/120200.793740:ERROR:zygote_communication_linux.cc(276)] Failed to send GetTerminationStatus message to zygote
QDBusAbstractAdaptor: Cannot relay signal KDEDModule::moduleDeleted(KDEDModule*): Pointers are not supported: KDEDModule*
QDBusAbstractAdaptor: Cannot relay signal KDEDModule::moduleDeleted(KDEDModule*): Pointers are not supported: KDEDModule*
QDBusAbstractAdaptor: Cannot relay signal KDEDModule::moduleDeleted(KDEDModule*): Pointers are not supported: KDEDModule*
QDBusAbstractAdaptor: Cannot relay signal KDEDModule::moduleDeleted(KDEDModule*): Pointers are not supported: KDEDModule*
QDBusAbstractAdaptor: Cannot relay signal KDEDModule::moduleDeleted(KDEDModule*): Pointers are not supported: KDEDModule*
QDBusAbstractAdaptor: Cannot relay signal KDEDModule::moduleDeleted(KDEDModule*): Pointers are not supported: KDEDModule*
QDBusAbstractAdaptor: Cannot relay signal KDEDModule::moduleDeleted(KDEDModule*): Pointers are not supported: KDEDModule*
QDBusAbstractAdaptor: Cannot relay signal KDEDModule::moduleDeleted(KDEDModule*): Pointers are not supported: KDEDModule*
QDBusAbstractAdaptor: Cannot relay signal KDEDModule::moduleDeleted(KDEDModule*): Pointers are not supported: KDEDModule*
QDBusAbstractAdaptor: Cannot relay signal KDEDModule::moduleDeleted(KDEDModule*): Pointers are not supported: KDEDModule*
QSocketNotifier: Invalid socket 8 with type Read, disabling...
QSocketNotifier: Invalid socket 10 with type Read, disabling...
KCrash: Application 'kwin_x11' crashing...
The X11 connection broke: I/O error (code 1)
XIO:  fatal IO error 4 (Прерван системный вызов) on X server ":50"
      after 21 requests (21 known processed) with 0 events remaining.
/usr/lib/kf5/bin/kwin_x11: FATAL ERROR while trying to open display :50
KCrash: Attempting to start /usr/lib/kf5/bin/kded5
KCrash: Application 'kded5' crashing...
KCrash: Attempting to start /usr/libexec/kf5/drkonqi
qt.qpa.xcb: could not connect to display :50
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

Available platform plugins are: wayland-org.kde.kwin.qpa, eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, xcb.

qt.qpa.xcb: could not connect to display :50
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

Available platform plugins are: wayland-org.kde.kwin.qpa, eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, xcb.

Ради интереса проверил тоже самое и на MATE. В п8 такой проблемы нет ни в одном окружении (кроме cinnamon)