WebConfig is a free open-source web server configuration management panel offering graphical management of Apache and Nginx, SSL certificates, and website configuration across major Linux distributions for budget-conscious webmasters and SMBs.
Created by Jamie Cameron in 1997, Webmin is one of the oldest open-source Unix/Linux system administration panels, free under the BSD license with about 1,000,000 yearly installations and 1,000+ modules covering users, services, packages, and file management.
Cockpit is a Red Hat-sponsored open-source web server management console (LGPL v2.1+) supporting Fedora, RHEL, Debian and Ubuntu, offering free management of system services, storage, networking, VMs and containers.