gistfile1.php

<?php
/**
 * Disable the "foo" custom post type feed
 *
 * @since 1.0.0
 * @param object $query
 */
function ja_disable_cpt_feed( $query ) {
	if ( $query->is_feed() && in_array( 'foo', (array) $query->get( 'post_type' ) ) ) {
		die( 'Feed disabled' );
	}
}
add_action( 'pre_get_posts', 'ja_disable_cpt_feed' );

Our custom post slug is templates. I've added the following to our child theme's functions.php, but the CPT feed is still there.

function mandoe_disable_cpt_feed( $query ) {
	if ( $query->is_feed() && in_array( 'templates', (array) $query->get( 'post_type' ) ) ) {
		die( 'Feed disabled' );
	}
}
add_action( 'pre_get_posts', 'mandoe_disable_cpt_feed' );

I've resaved the Permalinks, and the issue remains.

Help appreciated.