QtCreator & XServer

[sos1]

I've set up Qt on wsl2 with Ubuntu 20.04 and that's running and compiling, with mobaxterm supplying the xserver.
The problem is that when I run the program in qtcreator, the running application doesn't appear in the xserver window. The DISPLAY is set in the build and run settings to the windows IP address ":0".
How do I get to see the running application in an xserver window?
Jas

[sos1]

Btw, the application I'm running is an example supplied with Qt and I can see the process running.
Setting the "platform" to minimal or offscreen prevents a segfault.