The registration for a course can be fully automated. When a department or group is associated with a course, everyone in that group automatically gains access. As a user you don't have to go through any steps, you can just start.
By determining in advance who should complete which course, there is hardly any management effort required. Especially if a link has been made with Azure Active Directory. Of course it is also possible to link the courses to the user or to make users themselves responsible for registering for a course. Our experience is that the latter option is technically an option, but does not add anything to your security awareness goal. And you may achieve the opposite. Our advice is to link the courses to the departments as much as possible.