Mumble

Mumble is an open source, low-latency, encrypted, high quality voice chat software.

You can connect to your Mumble server on the regular Mumble port 64738. Clients to connect to Mumble from your desktop and Android devices are available.

Desktop Mumble GNU/Linux macOS Windows
Mobile Mumble App Store
Plumble F-Droid Play Store
Mumblefly App Store
Mumla F-Droid
Package Mumble
Debian: mumble