Wordpress - WordPress thinks my custom route is a 404

Manually setting is_404 = false; fixed my issue. However I'm not sure this is the best way to do it. I tried using the pre_get_posts filter instead without any luck.

Anyway, for anyone else in the same boat, you can do this to get rid of the 404 state:

public function add_response_template($template) {
  global $wp_query;
  if ( 'my_custom_url' === get_query_var( 'pagename' ) ) {
    $wp_query->is_404 = false;
    $template = trailingslashit( dirname( __FILE__ ) ) . 'templates/custom-page-template.php';
  }

  return $template;
}

And to update the document title (The stuff inside <title> in the <head> section) here's a snippet for making that work nicely too.

add_filter( 'document_title_parts', function($title_arr) {
  if ( 'my_custom_url' === get_query_var('pagename') ) {
    $title_arr['title'] = "Document title for my custom route";
  }

  return $title_arr;
}, 10, 1 );

If anyone knows of a better way please let me know.