Google Duo - Google's answer to Facetime, high-quality video calling on iOS and Android.

Mumble - Mumble is an open source, low-latency, high quality voice chat software primarily intended for use...

GoRemote - A free & simple yet powerful European based solution to go remote. Video & audio conferences, screen sharing & chat with end to end encryption. Keep your team close and productive

Discord - Step up your game with a modern voice & text chat app. Crystal clear voice, multiple server and channel support, mobile apps, and more.

Around - Find people to hang out with.

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.