magento-test/app/code/Magento/Customer/view/adminhtml/templates/tab/newsletter.phtml

<?php
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
?>
<?php /** @var \Magento\Customer\Block\Adminhtml\Edit\Tab\Newsletter $block */ ?>
<div class="entry-edit">
<?= $block->getForm()->getHtml() ?>
</div>
<?= $block->getChildHtml('grid') ?>