Purpur
Purpur is a drop-in replacement for Paper servers
...The project focuses on allowing administrators to modify gameplay mechanics, behaviors, and rules that are normally fixed in standard server implementations. Through a wide set of configuration settings, server operators can adjust how mobs behave, alter game mechanics, or enable experimental gameplay features that are not present in vanilla Minecraft. Purpur inherits performance improvements and plugin compatibility from the Paper ecosystem while adding its own enhancements and customization capabilities.