Install gir1.2-gtk-3.0 by entering the following commands in the terminal:
sudo apt update sudo apt install gir1.2-gtk-3.0
Description:
GTK+ graphical user interface library -- gir bindings
GTK+ is a multi-platform toolkit for creating graphical user interfaces. Offering a complete set of widgets, GTK+ is suitable for projects ranging from small one-off tools to complete application suites. . This package can be used by other packages using the GIRepository format to generate dynamic bindings.
Homepage: https://www.gtk.org/
Version: 3.22.30-1ubuntu1
Section: introspection