materio-d8/web/modules/custom/materio_home/includes/materio_home.inc

<?php

use Drupal\Core\Url;

function template_preprocess_materio_home(&$vars){
  $node_view_builder = \Drupal::entityTypeManager()->getViewBuilder('node');

  $vm = "default";
  $fpnode = $vars['frontpage_node'];
  $nvb_fpnode = $node_view_builder->view($fpnode, $vm);
  $vars['frontpage_node'] = $nvb_fpnode;

}