How do I render content "as is" from custom controller
Since this is a text area field, you need to specify a type of render element, processed_text.

$render_array['snippet'] = [
  '#theme' =&gt; 'webpart_snippet',
  '#type' =&gt; 'processed_text',
  '#text' =&gt; $node-&gt;field_content-&gt;value,
  '#format' =&gt; $node-&gt;field_content-&gt;format,
  '#prefix' =&gt; '&lt;div class="webpart_outer_wrapper"&gt;',
  '#suffix' =&gt; '&lt;/div&gt;',
];