Here is a polished description in English, adapted for version 1.21.1, keeping the exact meaning of the original text:
A simple mod designed to enable FTB Teams functionality for offline-mode servers on Minecraft 1.21.1.
On offline servers, certain functions of FTB Teams are disabled for offline players by default, as the original maintainers do not support offline mode (stating that users should "buy the game and run the server in online mode"). This mod restores that functionality.
Important:
If your server runs in offline mode (online-mode=false), every offline player on your server must install this mod on their client to ensure it works correctly.
