I am having this exact same issue! Came in after the weekend to my work computer and the layout has changed exactly like the above and I can't change it back. Even the search bar is the same showing <0w>.
I have no pending updates and I'd really like to change it back, this new interface is not great.
For some reason it won't let me upload a screenshot of my about outlook page but it says the below
Product Activated
Microsoft Outlook 2016
Update Options Button - Microsoft 365 and Office Updates
About Outlook Button - About Outlook