Seald - Keep your conversations secure, everywhere.
Mumble - Mumble is an open source, low-latency, high quality voice chat software primarily intended for use...
Crypho - End-to-end-encrypted messaging and file sharing
Discord - Step up your game with a modern voice & text chat app. Crystal clear voice, multiple server and channel support, mobile apps, and more.
Spike - Spike solves businesses' communication chaos by bringing together email, team chat, collaborative docs, and meetings, into one feed.
RaidCall - Free & Light. Setting up is fast and easy; with no need to rent or set up servers. Low CPU usage and minimum memory footprint allows for smooth, uninterrupted communication. im. Group Communication.