Display problems

[mmaka]

I tried running my project in the Ubuntu terminal and I keep getting this problem:

QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-username'
qt.qpa.screen: QXcbConnection: Could not connect to display
Could not connect to any X display.

Does anyone know why this is and how to solve it?

[Kent-Dorfman]

what do you get when you echo $DISPLAY ?
what is the output of xhost ?

What happens if you enter XDG_RUNTIME_DIR=/tmp {qtprogram} in the terminal?

[jsulm]

@mmaka Do you run X11? Wayland or something else? Do you try to run your app via VCN? More information is needed.