Founded in 2019, ZeroSSL is a modern certificate authority offering free DV SSL certificates with an intuitive web management interface, ACME protocol, and REST API — with over 5 million certificates issued, it's the most popular free SSL alternative to Let's Encrypt.
Ajenti is an open-source Linux server management panel created in 2012 by Russian developer Eugene Pankov, MIT-licensed and free with 8k+ GitHub stars, lightweight and plugin-rich for visual administration on low-end VPS.
Sentora is a free, open-source (GPLv3) web hosting control panel, a community fork of ZPanel that manages websites, databases, DNS, and email for multiple clients from a single installation - a zero-cost option for self-hosted shared hosting.