Registration Has Ended message

My suggestion would be to edit the Event Page (formerly called the Landing Page) at the time registration ends. That way you can control exactly what appears. There’s no way I’m aware if to do this in advance and automatically change when registration ends. 

To customize the "Registration has ended" message, check your event registration plugin or platform settings. Most platforms let you change the text through their options or code. The default message typically says, "Registration for this event has ended," but it can vary.