How do I render a  tag? I am using the following code.

public function buildForm(array $form, FormStateInterface $form_state) {
 $appDir = take_control_app_dir();
 $extpath = take_control_fb_ext_client_path();

 $validationString = take_control_random_string(20);
 $fbpath = take_control_client_path(drupal_get_path('module', 'fb') . '/fb.html?extpath=' . $extpath);
 $form = [
   'example one' =&gt; [
     '#markup' =&gt; '&lt;iframe src="www.google.com"&gt;&lt;/iframe&gt;'
   ],
   'take_control' =&gt; [
     '#markup' =&gt; '&lt;p&gt;iframe&lt;/p&gt;',     
   ],
 ];

 return $form;
}


The &lt;iframe&gt; tag is not rendered.

Is there any way to make it render?
Probably iframe is filtered in #markup. Use an inline_template instead:

  'example one' =&gt; [
    '#type' =&gt; 'inline_template',
    '#template' =&gt; '&lt;iframe src="{{ url }}"&gt;&lt;/iframe&gt;',
    '#context' =&gt; [
      'url' =&gt; 'www.google.com',
    ],
  ],