What is CLU? CLU (ChunkLoadersUltimate) is a plugin designed for Bukkit, Spigot, Paper, and Purper based servers to provide a simple and light weight chunk loading plugin to keep chunks loaded.
CLU is a basic and easy to use plugin to keep chunks loaded. It has toggleable chunk loader blocks. It keeps chunks loaded as long as a player is online, and if the chunk loader is enabled. No need for multi dimension chunk loaders! Just place a chunk loader block inside whatever chunk you want and boom! It's keeping the chunk loaded.
Tested versions: 1.16.5, 1.21.11. This leads me to assume all versions in between work.
To install CLU, first download the latest version, or which ever version suits your server. Then shutdown your server, put the plugin into the plugins folder, and restart your server. In the logs you should see, "ChunkLoadersUltimate enabled." If you see that, the plugin is working fine. Refer to the above headers to learn more about how to use and configure the plugin.
Check gallery for CLU showcases.

This plugin adds chunk loaders!