AmkMcAuth

AmkMcAuth Version 1.5.5 is updated to work MineCraft vs. 1.21.6+

AmkMcAuth is an authentication plugin. It requires players to register their account with a password and use that password to login, adding another layer of security to any server. (If you are using email registration: the player has to register his email address after wich AmkMcAuth sends a random password to that email address so the player can login using that password, and possibly change it afterwards).

This plugin also protects (to some extend, its not a replacement for whitelist) your server against the "Operation Copenheimer" bots/griefers as it adds an extra login/password layer on your server so the bots mark your server as "protected" and not as "open".

First-time Install+Setup:
Just drop the plugin in your plugins folder and (re)start the server.

AmkMcAuth works default "out of the box", no special configuration needed, meaning: your players need to register a password (first time) and log in using that password.
Using the Admin commands you can manualy manage players.

But, it can do much, much more, for more Info, follow this link to find out:
https://dev.bukkit.org/projects/amkmcauth and/or: https://dev.bukkit.org/projects/amkmcauth/pages