Qt 6.4+ : menubars not visible when accessing headless system remotely

Hello,

There is an ongoing issue with Qt 6 which causes menus to not be available whenever a Qt app is running on a headless system (e.g. a system with no screen attached).

For instance, it's easily reproducible with Qt Creator on a raspberry pi :

• Install Qt Creator on Debian Bookworm
• Run a VNC and X server or something like NoMachine NX
• Access the Raspberry desktop remotely
• Open Qt Creator and try to click in a menu : it won't show up.

Here are many reports of it on the internet:

https://forum.qt.io/topic/151912/menus-from-qmainwindow-menubar-not-showing-on-qt-6-4-0/32

https://github.com/raspberrypi/Raspberry-Pi-OS-64bit/issues/243

https://forums.raspberrypi.com/viewtopic.php?t=361474&start=25

etc.