Display long text fields as type text input not as textarea on node forms
Drupal textfield widget can only be applied to string fields.
https://git.drupalcode.org/project/drupal/blob/8.7.4/core/lib/Drupal/Core/Field/Plugin/Field/FieldWidget/StringTextfieldWidget.php#L9

However it's not a big deal to alter its definition and make it support long strings.

/**
 * Implements hook_field_widget_info_alter().
 */
function HOOK_field_widget_info_alter(array &amp;$info) {
  $info['string_textfield']['field_types'][] = 'string_long';
}


After having this done it should be possible to assign textfield widget to long text fields on "Manage form display" page.