MantisBT

MantisBT (Mantis Bug Tracker) occupies the exact same open-source, highly traditional space as Bugzilla, but it has historically been favored by teams who found Bugzilla's interface too terrifying to look at. Mantis provides a significantly cleaner, more intuitive web interface (though still highly utilitarian) while maintaining the completely free, PHP/MySQL self-hosted architecture. Its absolute biggest selling point is its "Simplicity and Speed of Deployment." Setting up a complex Jira server can take a dedicated IT team three weeks. A single junior developer can download Mantis, upload the PHP files to a basic GoDaddy web server, connect the database, and have a fully functioning, highly robust bug tracking system running globally in exactly 15 minutes. Because it is built on simple, universal PHP, it is incredibly easy to customize. If an engineering team needs Mantis to talk to a strange, highly proprietary internal piece of software, any basic web developer can open the source code and write a custom webhook plugin in an afternoon, making it a highly malleable tool for scrappy development shops.