Menubar issue with Unity

[pasbi]

When using Unity, the menu bar is broken:

1. Managers can have (and PropertyManager has) their own menu bar. This is implemented by a hack as menu bars are not officially supported for non-QMainWindows. I guess Unity does not detect MainWindow's menu bar as "master".
2. leaf-items do not show text. Only action-group items are displayed properly. Leaf-items are also implemented by a hack ("Sub-menus are platform-specific spaghetti code"), I guess there's some problem.

[pasbi]

since 1b16536, Managers shall not have menu bars anymore. Since then, the main menu bar is correctly displayed in Unity, too.
However, most actions (those which are implemented as QWidgetAction) are not displayed correctly (wrong size, no text, no icon).
The issue is clearly caused by Unity, not Xenial: the combination Gnome3@Xenial renders the actions correctly.
Since Unity is dead since a few years and I have no clue how to address this issue, I suggest you to replace Unity.