Install gir1.2-matepanelapplet-4.0 by entering the following commands in the terminal:
sudo apt update sudo apt install gir1.2-matepanelapplet-4.0
Description:
GObject introspection data for MATE panel
The MATE Panel is an essential part of the MATE Desktop, providing toolbar-like “panels” which can be attached to the sides of your desktop. They are used to launch applications and embed a number of other functions, such as quick launch icons, the clock, the notification area, volume controls and the battery charge indicator, and utilities ranging from weather forecast to system monitoring. . This package contains introspection data for MATE panel. . It can be used by packages using the GIRepository format to generate dynamic bindings.
Homepage: http://www.mate-desktop.org/
Version: 1.20.1-3ubuntu1
Section: universe/introspection