Need a current page's "Content Type" passed to a node.html.twig template (for a different content type) on page load, AND after ajax call
Well, here's what I came up with... and it's working as needed. If there are issues with this approach, please feel free to critique. My backend skills leave much to be desired. Thanks!

function custom_mods_preprocess_node(array &amp;$variables, $hook) {

// Get the current page's content type on page load
$node = \Drupal::routeMatch()-&gt;getParameter('node');
if ($node instanceof \Drupal\node\NodeInterface) {
  $variables['pageNodeType'] = $node-&gt;getType();
}

// Keeps the type available if an AJAX call happens 
if (\Drupal::routeMatch()-&gt;getRouteName() == 'views.ajax') {
  $previousUrl = \Drupal::request()-&gt;headers-&gt;get('referer');
  $fake_request = Request::create($previousUrl);
  $url_object = \Drupal::service('path.validator')-&gt;getUrlIfValid($fake_request-&gt;getRequestUri());
  if ($url_object) {
    $route_params = $url_object-&gt;getRouteParameters();
    $ent_id = $route_params['entity_id'];
    $node = \Drupal\node\Entity\Node::load($ent_id);
    $variables['pageNodeType'] = $node-&gt;getType();
  }
}