Hangouts Alternatives for Linux

Skype is an instant messaging and VOIP (Voice Over Internet Protocol) client to communicate with people in a distant place.

Pidgin is a free and open-source chat client which supports AIM, Google Talk, ICQ, XMPP protocols.

Telegram is a free cloud-based instant messaging platform.

Slack is a cloud-based team collaboration tool.

Tox is a peer-to-peer instant-messaging and video-calling protocol that offers end-to-end encryption.

Trillian is a proprietary multiprotocol instant messaging application.

Viber Free Messenger and Phone Calls.

Discord is a freeware proprietary VoIP application designed for gaming communities.

Signal is the most scalable encryption tool.

Jitsi (formerly SIP Communicator) is a free and open source multiplatform voice (VoIP), videoconferencing and instant messaging application.

Empathy is an instant messaging (IM) and voice over IP (VoIP) client which supports text, voice, video, file transfers, and inter-application communication over various IM protocols.

Wire is a cross-platform, encrypted instant messaging client created by Wire Swiss. It is available for iOS, Android, Linux, Windows, macOS and Web browser clients.

Franz is a free messaging app /former emperor of Austria, that combines chat & messaging services into one application.

Ring (SFLphone) is an open-source SIP-compatible softphone and instant messenger for Linux, Microsoft Windows, OS X and Android.

Gajim is an instant messaging client for the XMPP protocol which uses the GTK+ toolkit.

Matrix is an open protocol for real-time communication. It is designed to allow users with accounts at one communications service provider to communicate with users of a different service provider via online chat, Voice over IP, and Videotelephony.

Rambox is a free and Open Source messaging and emailing app that combines common web applications into one.

BigBlueButton is an open source web conferencing system.

Zulip is a chat and collaborative software.

QuteCom (WengoPhone) is a free-software SIP-compliant VoIP client.

Dialog Messenger is a handy and feature-rich enterprise multi-device messenger available for server or cloud.

Tkabber is a GPL instant messaging client for the XMPP protocol which uses the Tk toolkit for the GUI.

YakYak is a desktop chat client for Google Hangouts.

Toky is an automation platform.