I have a Galaxy 8 phone that I can customise the content of always on display in some limited way. I could not find any option to add the upcoming calender event to it. Is there any way to do that?
Go to settings. Then Lock screen and Security. Scroll down to Lock Screen and Always on Display. Select Information and FaceWidgets. Then select FaceWidgets. From there you can select "Today's Schedule" as a screen on Always on Display. (I have the Note 8, but I would imagine you'd do something similar or the same thing.)