Thank you! Yes, InputPanel was what was needed to make the VirtualKeyboard actually show on embedded (eglfs_kms or wayland). Then it also needs a y and width. And then it is always visible by default, so I guess need to bind visible: active.

The code shown on this page, i.e. without InputPanel, "just worked" on desktop (except the virtual keyboard was massive), but not embedded
https://doc.qt.io/qt-6/qtvirtualkeyboard-basic-example.html
and the "Detailed Description" here didn't really explain why/when to use it
https://doc.qt.io/qt-6/qml-qtquick-virtualkeyboard-inputpanel.html

@mrjj Yes, What I did was

QFontDatabase::addApplicationFont("/usr/share/fonts/truetype/Open_Sans/OpenSans-Regular.ttf");

and then select "Open Sans" on the QtDesigner

@SGaist Indeed :)

You have Mesa's EGL headers in /usr/include which get picked up in place of the Broadcom ones. This is not necessarily fatal but you need to add DEFINES += MESA_EGL_NO_X11_HEADERS in qtbase/src/plugins/platforms/eglfs/deviceintegration/eglfs_brcm/eglfs_brcm.pro