I did not have any luck with that fast beta version you mentioned. Did you use that with the new PB4 or the DB5 from yesterday? Do we know if they are the same build of Monterey?You might to get on the latest Beta of Outlook and that one will work. Had the same issue but with the Aug 10 Update Outlook is working and no beachballs anymore. You can get it when you subscribe to the BETA channel.
Outlook Version that works is: 16.53 (21081001)