Session is an end-to-end encrypted messenger that removes sensitive metadata collection, and is designed for people who want privacy and freedom from any forms of surveillance. … https://www.tromjaro.com/session-messenger/
RetroShare
Retroshare establish encrypted connections between you and your friends to create a network of computers, and provides various distributed services on top of it: forums, channels, chat, mail… … https://www.tromjaro.com/retroshare/