Unity System Settings > Appearance > Behavior > Show the menus for a window > In the window's title bar
2. Open an app with GNOME Headerbars that Ubuntu hasn't patched to remove the headerbar, such as Sudoku
What happens
============
The menu bar never shows up.
Suggestion #1
=============
Maybe Unity should implement the appmenu window button like is used in Ubuntu Budgie and is optionally available in GNOME Shell. To see the appmenu in Ubuntu 17.10+, use GNOME Tweaks to turn off Top Bar > Application Menu. You may want to log out and log back in.
1. Change this setting
Unity System Settings > Appearance > Behavior > Show the menus for a window > In the window's title bar
2. Open an app with GNOME Headerbars that Ubuntu hasn't patched to remove the headerbar, such as Sudoku
What happens
============
The menu bar never shows up.
Suggestion #1
=============
Maybe Unity should implement the appmenu window button like is used in Ubuntu Budgie and is optionally available in GNOME Shell. To see the appmenu in Ubuntu 17.10+, use GNOME Tweaks to turn off Top Bar > Application Menu. You may want to log out and log back in.