Install libcryptui-doc by entering the following commands in the terminal:
sudo apt update sudo apt install libcryptui-doc
Description:
UI library for OpenPGP prompts (documentation)
CryptUI is a library to manage OpenPGP prompts on GUI applications. . This package contains the HTML documentation and API reference for the CryptUI library.
Homepage: http://developer.gnome.org/libcryptui/
Version: 3.12.2-5
Section: universe/doc