AMP Disable ES Modules (unless enabled with query param)

amp-disable-esm-unconditionally.php

<?php
/**
 * AMP Disable ES Modules by Default plugin.
 *
 * @package   AMP_Disable_ESM
 * @author    Weston Ruter
 * @link      https://gist.github.com/westonruter/279bcb54336449ce55d8887fb0fcf5b9
 * @license   GPL-2.0-or-later
 *
 * @wordpress-plugin
 * Plugin Name: AMP Disable ES Modules by Default
 * Plugin URI: https://gist.github.com/westonruter/279bcb54336449ce55d8887fb0fcf5b9
 * Description: Disable the use of ES modules by the AMP Optimizer unless a <code>amp_optimizer_config</code> query parameter is provided to allow them.
 * Version: 0.1
 * Author: Weston Ruter
 * Author URI: https://weston.ruter.net/
 * License: MIT
 * Gist Plugin URI: https://gist.github.com/westonruter/279bcb54336449ce55d8887fb0fcf5b9
 */

use AmpProject\Optimizer\Transformer\RewriteAmpUrls;
use AmpProject\Optimizer\Configuration\RewriteAmpUrlsConfiguration;

if ( ! isset( $_GET['amp_esm_enabled'] ) ) {
	add_filter(
		'amp_optimizer_config',
		static function ( $config ) {
			$config[ RewriteAmpUrls::class ][ RewriteAmpUrlsConfiguration::ESM_MODULES_ENABLED ] = false;
			return $config;
		}
	);
}

Installation instructions: https://gist.github.com/westonruter/6110fbc4bef0c4b8c021a112012f7e9c