Spotlight and Finder can't search TextEdit files anymore?

I use TextEdit frequently for my writing, both personally and professionally. In Catalina, I would frequently use Finder to search for key words and phrases I've used in documents.

Since upgrading to Big Sur, Spotlight or Finder can't read the contents of any .RTF anymore, so they don't show up in search results unless the search term is in the filename.

I've re-indexed the relevant folders several times, and nothing works. I've run several tests, including Finder's advanced search, specifying "Content" in my query, but it seems like the new OS is completely blind to .RTF files.

My calls to support haven't yielded any concrete answers. Has this feature been removed? Can anyone else out there search within an .RTF file? Are there any solutions?