Thank you!
I made the changes via FTP. I could not test as the site requested .htpassword and the username/password combo didn’t work for it.
Anyways only one step is left, can you please re-create the index on test site? If all goes right, now every character should be converted from “œ” to “oe” format after indexing. If it works, then you can safely push the plugin folder to production.