apply_filters( 'relevanssi_search_url_prefix', string $url_prefix )
When doing spam blocking, Relevanssi looks for this URL prefix for pretty URL searches.
Parameters
$url_prefix
(string) The URL prefix for pretty URL search pages, default /search/.
More information
When checking for spam search queries, Relevanssi first looks at $_REQUEST['s'] to see if there’s something. This covers the searches done with ?s=search+term. For pretty URLs like /search/search+term this does not work, and another approach is needed. Relevanssi looks at the $_SERVER['REQUEST_URI'] next to see if it begins with /search/ and if it does, gets the search query there.
If your site uses a different prefix for the pretty URL searches, you can use this filter hook to make Relevanssi spam blocking understand that.
add_filter( 'relevanssi_search_url_prefix', function() { return '/recherche/'; } );