In System Preferences, I can set the time that "Do Not Disturb" begins but not when it ends. The end time remains stuck on "00:00". I think I may have triggered this because I wanted to have notifications go away all the time and I set the start time at "00:00" as well. Whatever the reason, every time I install a new app I get a stupid nag asking me whether I want to receive notifications for that app. Or does "Do Not Disturb" not make those go away? With Catalina, I didn't have that problem.