Taxonomy references field in users

It can be resolved by custom module.

Apply this patch https://www.drupal.org/project/user_csv_import/issues/3380676 ✨ Allows altering a user during importing Needs review .

Add code like:

/**
 * Implements hook_user_csv_import_create_user_alter().
 */
function custom_module_user_csv_import_create_user_alter(UserInterface &$user, $values): void {
  if ($user->hasField('field_department')
    && $values['field_department'] !== '') {
    $tid = custom_module_create_terms('person_department', [$values['field_department']]);
    $user->set('field_department', $tid);
    $user->save();
  }
}

/**
 * Create the terms.
 *
 * @param $vid
 * @param array $values
 *
 * @return array
 * @throws \Drupal\Component\Plugin\Exception\InvalidPluginDefinitionException
 * @throws \Drupal\Component\Plugin\Exception\PluginNotFoundException
 * @throws \Drupal\Core\Entity\EntityStorageException
 */
function custom_module_create_terms($vid, array $values = []): array {
  $terms = [];

  foreach ($values as $value) {
    if ($value != '') {
      $term = custom_module_get_tid_by_name($value, $vid);
      if ($term === FALSE) {
        $term = \Drupal::entityTypeManager()
          ->getStorage('taxonomy_term')
          ->create([
            'parent' => [],
            'name' => $value,
            'vid' => $vid,
          ]);

        $term->save();
      }
      $terms[] = $term;
    }
  }

  return $terms;
}

/**
 * Find term by name and vid.
 *
 * @param $name
 * @param $vid
 *
 * @return false
 * @throws \Drupal\Component\Plugin\Exception\InvalidPluginDefinitionException
 * @throws \Drupal\Component\Plugin\Exception\PluginNotFoundException
 */
function custom_module_get_tid_by_name($name = NULL, $vid = NULL) {
  $term = custom_module_get_term_by_name($name, $vid);

  return !empty($term) ? $term->id() : FALSE;
}

/**
 * Get term by name.
 *
 * @param $name
 * @param $vid
 *
 * @return false|mixed
 * @throws \Drupal\Component\Plugin\Exception\InvalidPluginDefinitionException
 * @throws \Drupal\Component\Plugin\Exception\PluginNotFoundException
 */
function custom_module_get_term_by_name($name = NULL, $vid = NULL): mixed {
  $properties = [];
  if (!empty($name)) {
    $properties['name'] = $name;
  }
  if (!empty($vid)) {
    $properties['vid'] = $vid;
  }

  $terms = \Drupal::entityTypeManager()
    ->getStorage('taxonomy_term')
    ->loadByProperties($properties);
  $term = reset($terms);

  return !empty($term) ? $term : FALSE;
}