The repository XxFluffyAsherxX/Eaglercraft-1.20.4-Updated- indicates it may include to allow the Eaglercraft client to connect. The community project, EaglerXServer , serves as a drop-in plugin for BungeeCord and Velocity proxies to facilitate this connection.
If you're asking about the part, here are a few possibilities of what you might mean: eaglercraft 120 updated