Empathy - Apps/Empathy - GNOME Wiki!
Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
Pidgin - Pidgin is an easy to use and free chat client used by millions. Connect to AIM, MSN, Yahoo, and more chat networks all at once.
Telegram X - Meet Telegram X for iOS and Android – two new official apps that offer more speed, longer batter life and smooth animations.
Trillian - Trillian is a decentralized and federated instant messaging platform that lets your whole company send private and group messages, keep tabs on what co-workers are doing, share files, and much more.
Unigram - The Telegram client for the Windows 10 platform, built by the community for the community.