Enable "Related Post" for a CPT

add_filter( 'astra_related_posts_supported_post_types', 'ast_add_related_posts_cpt_support' );

function ast_add_related_posts_cpt_support( $post_types ) {
    $post_types = array(
        'post',
        'my-cpt-1'
    );
    return $post_types;
}