So grateful, Bike-turkey - your fix of re-indexing the hard drive on Spotlight worked for me! I had migrated over from a 2015 Mac with Catalina to the new M1 Macbook Pro and thought at first it was an Outlook issue (I still run "old" Outlook, as I use an Exchange server for one email account and can't afford to have issues there, as mentioned previously on this board), but this board helped me see my search issue in both Outlook and File Finder was actually the SAME issue, not 2 issues: the Spotlight bug in Monterey. I did what you suggested above (go to System Preferences-Spotlight-Privacy, add hard drive to area not searched, then remove it), rebooting in between the adding of my hard drive to search exclusion (as you did) and removing it, then made sure my computer stayed out of sleep mode for at least an hour overnight to rebuild the index. This morning my life is MUCH better.
FYI, Microsoft support has a thread up that says Monterey 12.1 fixes the problem - https://support.microsoft.com/en-us/office/search-in-outlook-for-mac-returns-no-results-after-installing-macos-monterey-12-1-075c5f09-35db-4205-aba3-eea2f168c71b - this was NOT true for me. Also, as with folks above, I was running Outlook 16.57, and my system said I was up to date, so I couldn't easily get my hands on 16.58 to try that possible fix. So glad I tried this first. Hope Apple fixes it SOON. How frustrating.