Remove filter formats help text
Apparently you can't hook into the #process phase, but you can still do a #pre_render, from /Drupal/Core/Render/Renderer.php

// If the default values for this element have not been loaded yet, populate
// them.
if (isset($elements['#type']) &amp;&amp; empty($elements['#defaults_loaded'])) {
  $elements += $this-&gt;elementInfo-&gt;getInfo($elements['#type']);
}

// Make any final changes to the element before it is rendered. This means
// that the $element or the children can be altered or corrected before the
// element is rendered into the final text.
if (isset($elements['#pre_render'])) {
  foreach ($elements['#pre_render'] as $callable) {
    if (is_string($callable) &amp;&amp; strpos($callable, '::') === FALSE) {
      $callable = $this-&gt;controllerResolver-&gt;getControllerFromDefinition($callable);
    }
    $elements = call_user_func($callable, $elements);
  }
}


For example, to hide the element format of the body field of an article:

/**
 * Implements hook_form_alter().
 */
function mymodule_form_alter(&amp;$form, &amp;$form_state, $form_id) {
  $form['#pre_render'][] = 'mymodule_form_pre_render_body';
}

function mymodule_form_pre_render_body(array $element) {
  foreach (Element::children($element) as $key) {
    if ($key == 'body') {
      foreach (Element::children($element[$key]['widget']) as $widget) {
        $element[$key]['widget'][$widget]['format']['#access'] = FALSE;
      }
    }
  }

  return $element;
}