fix-login-page-style-on-buddyboss-theme.php

<?php
/**
 * Plugin Name: [Defender Pro] - Fix masked login URL page style on BuddyBoss theme
 * Author: Ohid @ WPMUDEV
 * Author URI: https://premium.wpmudev.org
 * License: GPLv2 or later
 */

if ( ! defined( 'ABSPATH' ) ) {
	exit;
} elseif ( defined( 'WP_CLI' ) && WP_CLI ) {
	return;
}

/**
 * Add the required  body class to the login page body classes to get the proper style
 *
 * @param array $classes gets the body classes
 * 
 * @return array
 */
function wpmu_login_body_class($classes)
{
    if (! isset($classes['login-split-page'])) {
        $classes[] = 'login-split-page';
    }

    return $classes;
}

add_filter('login_body_class', 'wpmu_login_body_class', 99, 1);