This extension works well for me. Indeed, I would strongly advise anyone who encounters any bug, either with the extension or with the main indexing program recoll itself, to contact the developer directly.
https://www.lesbonscomptes.com/recoll/support.html

I can speak from over a decade of repeated interaction with this developer that he is truly an exemplar in open source development Whenever I contact him about an issue with either the extension or the main program, he always respond courteously and effectively. All my bugs and feature requests over the decade, either of the extension or of recoll itself, have been resolved to my full satisfaction.

As with any complex piece of software, debugging often requires a back and forth, iterative process. If one has trouble with the extension, contact the developer via the methods listed in the link above and detail your bug and your system configuration. I am very confident your problem can be resolved as well as all mine over all these years!

Does not work at all, and causes ff to malfunction.