ProfileFieldSettings.php

<?php

namespace Drupal\user\Plugin\migrate\process;

use Drupal\migrate\MigrateExecutableInterface;
use Drupal\migrate\ProcessPluginBase;
use Drupal\migrate\Row;

/**
 * @MigrateProcessPlugin(
 *   id = "profile_field_settings"
 * )
 */
class ProfileFieldSettings extends ProcessPluginBase {
    
    /**
     * {@inheritdoc}
     */
    public function transform($type, MigrateExecutableInterface $migrate_executable, Row $row, $destination_property) {
        $settings = [];
        switch ($type) {
            case 'date':
                $settings['datetime_type'] = 'date';
                break;
        }
        return $settings;
    }

}