hellogl2 example crashs on Linux if swrast is not found

I have a simliar problem like https://bugreports.qt.io/browse/QTCREATORBUG-15728 

System

• Windows 10 (host) with Intel HD Graphics 4600 and Nvidia GeForce GT 730M
• Xming Version 7.7.0.36
• Ubuntu 18.04 (client) -> Let's name it UbuClient

Configuration

• Xming must be activated with  Accelerated OpenGL with WGL "AIGLX"

Steps to reproduce

• Connect via Xming to UbuClient
• Open QtCreator 4.9.1 from downloaded Qt 5.12.4 SDK
• Open Qt hellogl2 example
• Run the example
• Observe the console 

libGL error: No matching fbConfigs or visuals found
libGL error: failed to load driver: swrast
qt.glx: qglx_findConfig: Failed to finding matching FBConfig (8 8 8 8)
...
QOpenGLWidget: Failed to make context current
...
QOpenGLWidget: Failed to make context current
QOpenGLShaderProgram: could not create shader program
QOpenGLShader: could not create shader
Could not link shader program:
""
16:54:52: The program has unexpectedly finished.
16:54:52: The process was ended forcefully.

Further information

I tried to check why swrast (software rendering) could not be loaded. First I entered on UbuClient this:

find /usr -iname "*libGL.so*" -exec ls -l – {} +

Result:

lrwxrwxrwx 1 root root 14 May 10 14:17 /usr/lib/x86_64-linux-gnu/libGL.so -> libGL.so.1.0.0
lrwxrwxrwx 1 root root 14 May 10 14:17 /usr/lib/x86_64-linux-gnu/libGL.so.1 -> libGL.so.1.0.0
rw-rr- 1 root root 567624 May 10 14:17 /usr/lib/x86_64-linux-gnu/libGL.so.1.0.0

Then I check with "LIBGL_DEBUG=verbose glxgears > /dev/null" the errors:

libGL: Can't open configuration file /etc/drirc: No such file or directory.
libGL: Can't open configuration file /home-user/.drirc: No such file or directory.
libGL: Can't open configuration file /etc/drirc: No such file or directory.
libGL: Can't open configuration file /home-user/.drirc: No such file or directory.
libGL error: No matching fbConfigs or visuals found
libGL error: failed to load driver: swrast

And the command "glxinfo | grep render" returns:

libGL error: No matching fbConfigs or visuals found
libGL error: failed to load driver: swrast
direct rendering: No (If you want to find out why, try setting LIBGL_DEBUG=verbose)
GLX_MESA_multithread_makecurrent, GLX_MESA_query_renderer,
OpenGL renderer string: Intel(R) HD Graphics 4600

References

https://superuser.com/questions/563130/libgl-debug-verbose-not-working

https://askubuntu.com/questions/541343/problems-with-libgl-fbconfigs-swrast-through-each-update

https://debianforum.de/forum/viewtopic.php?t=171404

https://forum.qt.io/topic/40538/failed-to-load-driver-swrast/4

https://www.mesa3d.org/envvars.html

Surprise Surprise

If I rename the qt plugin folder xcbglintegrations to xcbglintegrations_bak, then hellogl2 doesn't crash but the rendering is not working anymore with the output:

XcbIntegration: Cannot create platform OpenGL context, neither GLX nor EGL are enabled
QXcbIntegration: Cannot create platform OpenGL context, neither GLX nor EGL are enabled
QOpenGLWidget: Failed to create context
QXcbIntegration: Cannot create platform OpenGL context, neither GLX nor EGL are enabled
QOpenGLWidget: Failed to create context
QXcbIntegration: Cannot create platform OpenGL context, neither GLX nor EGL are enabled
qt.qpa.backingstore: composeAndFlush: QOpenGLContext creation failed
qt.qpa.backingstore: composeAndFlush: makeCurrent() failed