Jitsi (formerly SIP Communicator) is a free and open source multiplatform voice (VoIP), videoconferencing and instant messaging application. Developed by University of Strasbourg (France), plus many others.
License: Open Source
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. Developed by Matrix.org
License: Open Source
Matrix.org is a decentralized communication platform that emphasizes security and interoperability, making it suitable for complex communication needs. In contrast, Jitsi is a user-friendly video conferencing tool that excels in simplicity and ease of use, making it ideal for quick and straightforward meetings.