Include Lessons in search results using the default module in the Courses for Membership Add On for Paid Memberships Pro.

include_pmpro_courses_lessons_in_search.php

<?php
/**
 * Include Lessons in search results using the default module in the Courses for Membership Add On for Paid Memberships Pro.
 * 
 * You can add this recipe to your site by creating a custom plugin
 * or using the Code Snippets plugin available for free in the WordPress repository.
 *
 */
function include_pmpro_courses_lessons_in_search($args, $post_type) {
	if ( $post_type == 'pmpro_lesson' ){
		$args['exclude_from_search'] = false;
	}
	return $args;
}
add_filter('register_post_type_args', 'include_pmpro_courses_lessons_in_search', 10, 2);