I asked the MS tech representative about removing Office 365, saving my Outlook (using the app deletion facility in Clean my Mac, so that all the service files get removed). He recommended against doing this as I would most likely lose my Outlook messages Database. This is stored at user/library/group containers/UBF8T346G9.Office/Outlook/Outlook 15 Profiles/Username Profile/Data/Messages. These are a series of folders in date order not a monolithic single incremental database file as in the past. They might be difficult to reinstall and get a new version of Office to recognise them. The MS technician felt that all I would be likely to achieve by removing and reinstalling is to clear my caches, where there are far simpler ways to do this.
Sadly this blind shotgun approach of delete and reinstall is too frequently the suggestion when a programming problem arises instead of finding what the real issue is. Something in the 10.15.5 supplemental caused this problem and Apple and Microsoft really do need to liaise and find what it is, then send out a fix (maybe both something from Apple and an update from MS), instead of throwing this back at their customers.