Include a part template on specific node page
If you want override page.html.twig for special node 2. You can try this code

{% if node.id == '2' %}
   {% include directory ~ '/templates/parts/custom_html.html.twig' %}
{% endif %}


if other template you need process in your function theme first:

YOUR_THEME_process_FUNCTION_THEME(&amp;$vars) {
  if ($node = \Drupal::routeMatch()-&gt;getParameter('node')) {
    $vars['node'] = $node;
  }
}