If you have all updates installed, you should have 2211 (or higher) -
Go to File > Options > Advanced, and remove the check from the option to Show apps in Outlook. It's at the top - uncheck it to revert the bar to the bottom. Then restart Outlook!
This is only a temporary solution though - so vote for and comment on tone or both of these suggestions - hopefully they will add a permanent solution for people who want to remove it.
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Do not change the overrides key if you have the check box in Options (above)
If you don't have the option, you can add a string value named Microsoft.Office.Outlook.Hub.HubBar to the key below and set it to False, then restart Outlook. (It's only a short-term fix, although right now, we don't know how short term.)
HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\ExperimentConfigs\ExternalFeatureOverrides\outlook
If you don't want to edit the registry, I have a ready to use reg file at the end of this article -