bbPress.org

you can add the bbpress post type to the default wordpress search.

copy this into your child theme functions.php or a functionality plugin

/**
 * Include bbPress 'topic' custom post type in WordPress' search results
 */
function ntwb_bbp_topic_cpt_search( $topic_search ) {
	$topic_search['exclude_from_search'] = false;
	return $topic_search;
}
add_filter( 'bbp_register_topic_post_type', 'ntwb_bbp_topic_cpt_search' );

/**
 * Include bbPress 'reply' custom post type in WordPress' search results
 */
function ntwb_bbp_reply_cpt_search( $reply_search ) {
	$reply_search['exclude_from_search'] = false;
	return $reply_search;
}
add_filter( 'bbp_register_reply_post_type', 'ntwb_bbp_reply_cpt_search' );

function ntwb_bbp_forum_cpt_search( $forum_search ) {
$forum_search['exclude_from_search'] = false;
return $forum_search;
}
add_filter( 'bbp_register_forum_post_type', 'ntwb_bbp_forum_cpt_search' );