setWindowFlag(Qt::WindowMaximized) does not work properly on Ubuntu 24

showMaximized() and, more precisely, setWindowFlag(Qt::WindowMaximized) do not work properly on Ubuntu 24 X11.

The window state is briefly set to Qt::WindowMaximized before being ignored and reverted to Qt::WindowNoState. Several tests check this and interpret the Qt::WindowMaximized flag as positive before it is ignored and reset to Qt::WindowNoState. This behavior is easily observable by pausing after showMaximized()/setWindowFlag.

Upon investigation, it seems that the WindowManager ignores the Qt::WindowMaximized flag of a window if it isn't already the active window. The flag is received, ignored, and then dismissed.

Find a way to make setWindowFlag(Qt::WindowMaximized) work as intended on Ubuntu 24.