Index: VirtualBox-6.1.8/src/VBox/Frontends/VirtualBox/src/main.cpp
===================================================================
--- VirtualBox-6.1.8.orig/src/VBox/Frontends/VirtualBox/src/main.cpp
+++ VirtualBox-6.1.8/src/VBox/Frontends/VirtualBox/src/main.cpp
@@ -669,6 +669,8 @@ extern "C" DECLEXPORT(int) TrustedMain(i
         /* Make sure multi-threaded environment is safe: */
         if (!MakeSureMultiThreadingIsSafe())
             break;
+        /* Force using Qt platform module 'xcb', we have X11 specific code: */
+        RTEnvSet("QT_QPA_PLATFORM", "xcb");
 #endif /* VBOX_WS_X11 */
 
         /* Console help preprocessing: */