Two new dark themes are supported, dark grey theme and black theme. You can change your current theme by going to any Office application File menu –> Account –> Office theme.
Improved inking support for all Office apps
New Excel features like new chart types, 2D maps, timelines, PowerPivot and PowerQuery improvements.
A Focus Mode to let you concentrate on your writing by hiding everything including menus in Microsoft word.
Focused Inbox in Outlook to show important emails on top of everything else.
Microsoft Outlook 2019 does not include modern authentication protocols which I was expecting. I’m using Mailbird as my default mail application instead of Outlook

AND MUCH MORE!