MBZ1_ I found the following link which solves the problem (at least for now!) You click on the "apps" tab in the moved ribbon on the left, go to options > advanced > and uncheck "show apps". Then restart your outlook and the ribbon will be back on the bottom:
https://techcommunity.microsoft.com/t5/outlook-global-customer-service/new-location-for-the-mail-calendar-people-and-other-modules/ba-p/3596278