The message indicating that Ars Nouveau support dynamic light is shown every world launch.
The setting showSupporterMessage is not set to false automaticly and even if it set to false manually, the message is still shown.
In 1.19.2 latest version : 3.17.10.

Show supporter message is for patrons, you would be looking for informLights. That however was also bugged, and is fixed next version.