Install addressmanager.app by entering the following commands in the terminal:
sudo apt update sudo apt install addressmanager.app
Description:
Personal Address Manager for GNUstep
This package constitutes a personal address manager for the GNUstep software system. It allows archiving complete personal contact information, organizing contacts in groups, integration with other software such as mail clients and sharing address information with other users over the network.
Homepage: http://www.nongnu.org/gap/addresses
Version: 0.4.8-3
Section: universe/mail