FreePBX is a web-based open source GUI (graphical user interface) that controls and manages Asterisk (PBX), an open source communication server.

VitalPBX is described as 'Full-feature PBX (phone system) based on Linux and Asterisk. VitalPBX is extremely easy to use, fast and secure. VitalPBX is free to use, including for commercial use, with no limitations of the amount of users' and is a IP PBX system in the social & communications category. There are five alternatives to VitalPBX for Linux, Raspberry Pi OS and Raspberry Pi. The best VitalPBX alternative is FreePBX, which is both free and Open Source. Other great apps like VitalPBX are Elastix, The Incredible PBX, PBX in a Flash and Ivoz Provider.
FreePBX is a web-based open source GUI (graphical user interface) that controls and manages Asterisk (PBX), an open source communication server.

More than a PBX, with Elastix you can communicate with your customers through voice, video and live chat from anywhere. Built-in video conferencing, website live chat and smartphone apps, ensure your agents remain productive through one unified mobile solution.

Incredible PBX is a secure and feature-rich implementation of the Asterisk® PBX. By rethinking the PBX security model from the ground up.

PBX in a Flash is a PBX system based on Asterisk, FreePBX and CentOS, coming as an ISO download. A two stage installation process allows for more flexibility for the installation of the PBX specific components.
IvozProvider supports multiple management levels, from Global platform administrator to final user, each of them having its own web interface with visibility to perform configuration tasks.