This tool allows for grepping files in a set of Org directories,
formatting the results as a separate Org buffer.  This buffer is
assorted with a few specific navigation commands so it works a bit
like M-x rgrep.  Optionally, the tool may simultaneously search
Unix mailboxes, Gnus mailgroups, or other textual files.

See https://sr.ht/~minshall/org-grep.