QT6 (Wayland): TMainMenu is duplicated on the designer surface.

• Lazarus 3.99 (rev main_3_99-1962-g0a7ff2fb3d)

• FPC 3.2.2 x86_64-linux-qt6

• Operating System: openSUSE Tumbleweed 20240503

• AnchorDocking and Docked Form Editor installed.

• KDE Plasma Version: 6.0.4

• KDE Frameworks Version: 6.1.0

• Qt Version: 6.7.0

• Graphics Platform: Wayland

What happens

At design-time, a TMainMenu instance dropped onto a form is duplicated. It displays both a faux menu bar and the real one, with subsequent controls shifted downward.

This does not occur at run-time.