Add Post Kinds for Wordpress kinds as a prefix to titles in RSS. https://danq.me/2020/03/01/post-kinds-rss/

wp-post-kinds-prefix-kind-in-rss.php

<?php

// Make titles in RSS feed be prefixed by the Kind of the post.
function add_kind_to_rss_post_title(){
	$kinds = wp_get_post_terms( get_the_ID(), 'kind' );
	if( ! isset( $kinds ) || empty( $kinds ) ) return get_the_title(); // sanity-check.
	$kind = $kinds[0]->name;
	$title = get_the_title();
	return trim( "[{$kind}] {$title}" );
}
add_filter( 'the_title_rss', 'add_kind_to_rss_post_title', 4 ); // priority 4 to ensure it happens BEFORE default escaping filters.