themes-wordpress/portia/patterns/hidden-404.php

<?php
/**
 * Title: 404
 * Slug: portia/hidden-404
 * Inserter: no
 */

declare( strict_types = 1 );
?>

<!-- wp:heading {"level":1,"fontSize":"large"} -->
<h1 class="wp-block-heading has-large-font-size"><?php echo esc_html__( 'Page Not Found', 'portia' ); ?></h1>
<!-- /wp:heading -->

<!-- wp:paragraph -->
<p><?php echo esc_html__( 'The page you are looking for does not exist, or it has been moved. Please try searching using the form below.', 'portia' ); ?></p>
<!-- /wp:paragraph -->