Multi rss feed on wordpress

If the custom post type is publicly available and in the main query, you should be able to put /feed after the Site URL to get all the published content.

I found the solution here: https://www.wpbeginner.com/wp-tutorials/how-to-add-custom-post-types-to-your-main-wordpress-rss-feed/#comment-174731

function myfeed_request($qv) {
	if (isset($qv['feed']) && !isset($qv['post_type']))
		$qv['post_type'] = array('post', 'story', 'books', 'movies');
	return $qv;
}
add_filter('request', 'myfeed_request');