Make variables created in preprocess_page hook available to content type templates
I was able to accomplish this by placing the code into the preprocess node hook instead of the preprocess page. Like so

mytheme.theme

function mytheme_preprocess_node(&amp;$variables){
    $myblock = \Drupal::service('plugin.manager.block')-&gt;createInstance('myblockid',[]);
    $variables['myblock'] = $myblock-&gt;build();