To enable iframe loading of your RISE website on external website, please comment out a config in

app/Config/Filters.php line#78

// 'secureheaders',

Full code block: 

    public array $globals = [
        'before' => [
            // 'honeypot',
            // 'csrf',
            // 'invalidchars',
        ],
        'after' => [
            // 'honeypot',
            // 'secureheaders',
        ],
    ];