With recent updates of Firefox (78) and Thunderbird (68.8) all menus have vanished from the system default place for menus. The menus should show in the menu bar (top of the screen) or in the window's title bar, according to the users system settings.
But now there are only 2 ways to access the menu: The menu button on the right side of the window, which is a hassle to go through with many sub menus, and to display the menu permanently inside the Thunderbird window, which is ugly and a waste of space.
Making the menu show by pressing the Alt key does not work any more too.
How can I get back the menus in practical and elegant "Unity-style"?