Sebafaim

Thanks !

I made it works for product tags too, my code if anyone need it :

add_filter('woof_text_search_query', function($where, $woof_text) {
 
    global $wpdb;

	$product_ids = [];

	//Search by ACF field
	$product_acf = $wpdb->get_results("
	SELECT posts.ID
	FROM $wpdb->posts AS posts
	LEFT JOIN $wpdb->postmeta AS postmeta ON ( posts.ID = postmeta.post_id )
	WHERE posts.post_type IN ('product')
	AND postmeta.meta_key = 'champs_de_recherche'
	AND (postmeta.meta_value LIKE '%$woof_text%')", ARRAY_N);

	if (!empty($product_acf)) {
		foreach ($product_acf as $v) {
	        $product_ids[] = $v[0];
	    }
	}

	//Search by product tags name
	$product_term = $wpdb->get_results("
	SELECT posts.ID
    FROM $wpdb->posts AS posts, $wpdb->term_relationships as term_relationships, $wpdb->terms as terms
    WHERE posts.ID = term_relationships.object_id
    AND terms.term_id = term_relationships.term_taxonomy_id
    AND terms.name LIKE '%$woof_text%'", ARRAY_N);

	if (!empty($product_term)) {
		foreach ($product_term as $v) {
	        $product_ids[] = $v[0];
	    }
	}

	if (!empty($product_ids)) {
		$product_ids_string = implode(',', $product_ids);
		$where .= " OR $wpdb->posts.ID IN($product_ids_string)";
	}
 
    return $where;
}, 99, 2);