Signal is a free software messenger for mobile (Android and iOS) and desktop (Windows, GNU/Linux, macOS). In many privacy-oriented web pages you could find, Signal is recognized as a good alternative to WhatsApp. It is recommended by PrivacyTools.io, MyShadow.org, Sven Taylor's RestorePrivacy.com (last checked 30 June 2018). What's more awesome is it provides desktop application for Ubuntu GNU/Linux. This tutorial explains how to install (and also uninstall) Signal Desktop on Ubuntu.