amp-auto-lightbox-disable.php

<?php
/**
 * AMP Auto-Lightbox Disable plugin bootstrap.
 *
 * @package   Google\AMP_Auto_Lightbox_Disable
 * @author    Weston Ruter, Google
 * @license   GPL-2.0-or-later
 * @copyright 2021 Google Inc.
 *
 * @wordpress-plugin
 * Plugin Name: AMP Auto-Lightbox Disable
 * Plugin URI: https://gist.github.com/westonruter/b6691407af1648b402b09371a9faf7f0
 * Description: Addresses <a href="https://github.com/ampproject/amp-wp/issues/5122">amp-wp#5122</a> by adding the <code>data-amp-auto-lightbox-disable</code> attribute to the <code>body</code>.
 * Version: 0.1
 * Author: Weston Ruter, Google
 * Author URI: https://weston.ruter.net/
 * License: GNU General Public License v2 (or later)
 * License URI: http://www.gnu.org/licenses/gpl-2.0.html
 * Gist Plugin URI: https://gist.github.com/westonruter/b6691407af1648b402b09371a9faf7f0
 */

namespace Google\AMP_Auto_Lightbox_Disable;

add_filter(
	'amp_content_sanitizers',
	function ( $sanitizers ) {
		require_once __DIR__ . '/Sanitizer.php';
		$sanitizers[ __NAMESPACE__ . '\Sanitizer' ] = [];
		return $sanitizers;
	}
);

Sanitizer.php

<?php
/**
 * Sanitizer file.
 *
 * @package Google\AMP_Auto_Lightbox_Disable
 */

namespace Google\AMP_Auto_Lightbox_Disable;

use AMP_Base_Sanitizer;

/**
 * Class Sanitizer
 */
class Sanitizer extends AMP_Base_Sanitizer {

	/**
	 * Add the data-amp-auto-lightbox-disable attribute to the body.
	 */
	public function sanitize() {
		$this->dom->body->setAttributeNode( $this->dom->createAttribute( 'data-amp-auto-lightbox-disable' ) );
	}
}

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