drupal_module__reinstall/src/EventSubscriber/UserPreImport.php

<?php

namespace Drupal\reinstall\EventSubscriber;

use Drupal\migrate\Event\MigrateEvents;
use Drupal\migrate\Event\MigrateImportEvent;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;

class UserPreImport implements EventSubscriberInterface {

  public static function getSubscribedEvents() {
    return [
      MigrateEvents::PRE_IMPORT => 'onPreImport',
    ];
  }

  public function onPreImport(MigrateImportEvent $event) {
    /** @var \Drupal\reinstall\Plugin\migrate\source\ReinstallUserSource $plugin */
    $plugin = $event->getMigration()->getSourcePlugin();
    $plugin->records = array_filter($plugin->records, [$this, 'filter01']);
    return;
  }

  /**
   * Skip users 0 and 1 in imports, as they are core-provided.
   *
   * @param array $record
   *   The description of a user entity.
   *
   * @return bool
   *   Include it (1) or filter it (0).
   */
  public function filter01(array $record) {
    $ret = ($record['uid'] ?? 0) > 1;
    return $ret;
  }

}