You can add global prefix to all join/leave message through the config. By adding these two lines:

custom_join_message_prefix: ""
custom_leave_message_prefix: ""

The plugin is now compatible with 1.21.1

Support for 1.20.
You can now set messages of other players directly through commands.
Added support for tab-autocompletion.
Default join/leave message can be set through config file.
Show command will preview colors.

Added 1.16 HEX colour codes support, updated plugin for 1.16