Enable landscape (desktop) support for stories that have the 'landscape' tag. Requires AMP plugin 1.2+.

amp-story-supports-landscape.php

<?php
/**
 * Plugin Name: AMP Story Supports Landscape
 *
 * @package   AMP_Story_Supports_Landscape
 * @author    Weston Ruter, Google
 * @license   GPL-2.0-or-later
 * @copyright 2019 Google Inc.
 *
 * @wordpress-plugin
 * Plugin Name: AMP Story Supports Landscape
 * Description: Enable landscape (desktop) support for stories that have the 'landscape' tag.
 * Plugin URI:  https://gist.github.com/westonruter/2ea25735be279b88c6f0946629d0240c
 * Version:     0.1.0
 * 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
 */

add_filter(
	'amp_story_supports_landscape',
	function ( $supports, $post ) {
		if ( has_tag( 'landscape', $post ) ) {
			$supports = true;
		}
		return $supports;
	},
	10,
	2
);

Thank you. This provides a useful feature in our testing of AMP Stories.