Aternos Team, The plugin Project korra is only limited to only v1.8.4 or Minecraft version 1.9, and we need to run different plugins to perfect our server.
The newest Project Korra version is v1.8.9 and allows it to work on 1.12+
ProjectKorra v1.8.9: https://projectkorra.com/projectkorra-core/
Note: I understand it isn't from Bukkit dev nor spigot (Only v1.8.4) However people enjoy 1.12+
