Install libgimp2.0-doc by entering the following commands in the terminal:
sudo apt update sudo apt install libgimp2.0-doc
Description:
Developers' Documentation for the GIMP library
This package contains the HTML documentation for the GIMP library in /usr/share/gtk-doc/html/ .
Homepage: https://www.gimp.org/
Version: 2.8.22-1
Section: universe/doc