Minestom is a Java API for making custom Minecraft servers. It doesn't contain vanilla functionality by default however it is designed so people can create their own behaviours for things - useful for Minigame servers.

Minestom does not have an extension / plugin loader since Minestom is meant to be compiled as a dependency into an existing application - this means MapModCompanion should follow a similar principle. You can look at MinestomPVP for an example on how to do this.

Minestom does support sending plugin messages (which MapModCompanion rely on) so it is possible to port MapModCompanion to Minestom.

Looks interesting! I'll definitely look into this