Mail Flagged Folder not Working in Sonoma 14.5

After updating to Sonoma 14.5, Apple's Mail's "Flagged" folder now has no emails in it. The search bar also no longer works, returning no results for any input.

I have restarted the app, rebuilt the mailboxes, and wiped and rebuilt the Spotlight database. Several times in various orders. None of that has restored functionality. Any other ideas?

Update: after the steps above, there is a new behavior: after entering a search term, the lower left corner does state "indexing..." for up to a minute. Then it disappears, with no results shown, but the search term still left in the search field.