It would be perfect that this plugin can also remove or hide the Activity link on the homepage side bar, so that this feature could be completely invisible.
I did it all wrong. There is a more efficient way to achieve what I planned to achieve with that plugin.
Basically you do not need a plugin at all. You only have to revoke the "Garden.Activity.View" permission for all views and add $Configuration['Garden'][Profile']['ShowActivities'] = false; to the /conf/config.php
Since Vanilla admins always have all permissions, you cannot revoke that permission for admins. Therefore you should check your forum after those changes by visiting your forum as a guest.
$Configuration['Garden'][Profile']['ShowActivities'] = false;
It might be needed to delete the files from /cache/Smarty/compiled
@R_J Actually that is also what I have done, and I found that the only part missing is the side bar link, in order to hide it from visitors completely. Probably what this plugin could do instead is to set it invisible through CSS?