appmenu-qt5 software package provides application menu for Qt5, you can install in your Ubuntu 16.04 LTS (Xenial Xerus) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install appmenu-qt5
appmenu-qt5 is installed in your system.
Make ensure the appmenu-qt5 package were installed using the commands given below,
$ sudo dpkg-query -l | grep appmenu-qt5 *
You will get with appmenu-qt5 package name, version, architecture and description in a table
| Distro | Ubuntu 16 04 lts xenial xerus |
| Section | KDE |
| Package | appmenu-qt5 |
| Version | 0.3.0+16.04.20151130-0ubuntu1 |
| Description | application menu for Qt5 |
| Sub Section | KDE |