No need to make this complicated. All that is necessary to start subscribing students is to enter a valid ConvertKit API key and secret, select the correct ConvertKit Form and create your segments with one click!
When enabled for a course, a prompt to subscribe to your newsletter will display during course registration for new students. If they’re logged in, all they need to do is click the button!
Every course which exists on your LearnDash site will generate a new tag within your chosen ConvertKit Form. This will allow you to very easily send communications to students enrolled in particular courses.