Notifications in wordpress in the frontend? For example, a new comment notification?

Question

Notifications

Please tell me how you can implement notifications in wordpress in the frontend (not in the admin). For example, the user left a comment under a post, and the number of new comments is shown to the author of the post in a certain place?
Email notifications are not the same. Maybe there are ready-made plugins already, but I'm just too blind that I couldn't find them?