I meet this situation as i wanted to add some hard coded text bevor the pagination table. It is just a demonstration how to render multiple TWIG templates within one return and can be useful to add third party code like external services (RSS, Webservices …)

$template['my_custom_html_content_headline'] = [
										'#theme' => 'custom_html_content_page',
										'#html' => t('<h1>Headline</h1>'),
										];
$template['my_custom_html_content_text'] = [
										'#theme' => 'custom_html_content_page',
										'#html' => t('<p>Lorem ipsum ...</p>'),
										];							
return $template;

$template['my_custom_html_content_headline'] = [

'#theme' => 'custom_html_content_page',

'#html' => t('<h1>Headline</h1>'),

];

$template['my_custom_html_content_text'] = [

'#theme' => 'custom_html_content_page',

'#html' => t('<p>Lorem ipsum ...</p>'),

];

return $template;

The “custom_html_content_page” template theme should be defined in mymodule.module file, something like:

<?php

/**
 * Implements hook_theme().
 */
function mymodule_theme() {

	$templates = array('custom_html_content_page' => array(
													'variables' => ['html' => NULL],
													'template' => 'custom_html_content',
													),
						
					);


  return $templates;
									
}

<?php

/**

* Implements hook_theme().

function mymodule_theme() {

$templates = array('custom_html_content_page' => array(

'variables' => ['html' => NULL],

'template' => 'custom_html_content',

);

return $templates;

}

And finally the TWIG template in the templates folder:

{{html}}

OUTPUT:

Headline

Lorem ipsum …