Unity-like HUD (Heads Up Display) feature which allows searching through application menus.Qt4 applications don't seem to be supported, at least in a default Ubuntu 18.04 setup (it can probably be done by exporting some env variable, but I don't think it's worth it given that it supports Qt 5 by default). This includes Gtk+ 2, Gtk+ 3, Qt 5 applications, Firefox, LibreOffice, and so on. It makes use of Unity GTK Modules, so it supports the same applications as the Unity global menu (AppMenu).

Check out its known issues section before using it. Since it's beta software, Gnome Global Menu extension is not considered stable. The instructions in this article won't work on Wayland. I only tested the Gnome Global AppMenu extension on X.Org (which is default in Ubuntu 18.04) though. The extension developer announced it discontinued the project a while back, but he changed his mind back in January 2018, when he successfully added support for Wayland. The extension also provides support for HUD menus so you can search in an application's menus. Gnome Global AppMenu is a Gnome Shell extension that's currently in beta, which implements Ubuntu Unity's global menu to Gnome Shell.

How to uninstall unity from mac