Install libpanel-applet-dev by entering the following commands in the terminal:
sudo apt update sudo apt install libpanel-applet-dev
Description:
library for GNOME Panel applets - development files
This package provides the include files and static library for the GNOME Panel applet library functions.
Homepage: https://wiki.gnome.org/Projects/GnomePanel
Version: 1:3.26.0-1ubuntu5
Section: universe/libdevel