Views exposed filter example. README.md file is not up to date.

Hi, I think the problem is mainly, that a keyvalue is needed to be saved on the backend possibly for security reasons.

$key_value_storage = \Drupal::service('keyvalue')->get('entity_autocomplete');
if (!$key_value_storage->has($selection_settings_key)) {
  $key_value_storage->set($selection_settings_key, $selection_settings);
}

And a the url should be generated this way:

$url = Drupal\core\Url::fromRoute(
  'autocomplete_deluxe.autocomplete',
  $route_parameters,
  ['absolute' => TRUE]
  )->getInternalPath();

With these modifications it worked for me.