themes-wordpress/lettre/patterns/hidden-subscription-form.php

<?php
/**
 * Title: Subscription form
 * Slug: lettre/hidden-subscription-form
 * Inserter: no
 */
?>

<!-- wp:group {"layout":{"type":"constrained"}} -->
<div class="wp-block-group"><!-- wp:jetpack/subscriptions {"buttonBackgroundColor":"primary","textColor":"secondary","fontSize":"0.9rem","customFontSize":"16px","borderRadius":50,"borderColor":"primary","className":"is-style-compact"} /--></div>
<!-- /wp:group -->