Stoat

Stoat is a free and open-source, user-first communication platform and instant messaging service. Designed as an alternative to proprietary services like Discord, Stoat allows users to communicate through text, voice, and media within organised communities called "servers". The platform is notable for its emphasis on privacy, its use of the Rust programming language for its back-end, and its support for self-hosting. Stoat is available on Windows, Linux, macOS, and Android, with an iOS app currently in development.

Excerpt from Wikipedia: Stoat (software). Content available under CC-BY-SA 4.0.