This plugin is a Gutenberg compatibility layer for the reCAPTCHA Jetpack plugin v0.2.2: https://wordpress.org/plugins/recaptcha-jetpack/

recaptcha-jetpack-compat.php

<?php
/**
 * Plugin Name: reCAPTCHA Jetpack Gutenberg Compatibility
 * Description: Adds reCAPTCHA to Jetpack Gutenberg forms.
 * Version: 1.0.0
 * Author: Cory Hughart
 * Author URI: https://coryhughart.com
 * License: GPLv2 or later
 *
 * This plugin is a Gutenberg compatibility layer for the reCAPTCHA Jetpack plugin v0.2.2: https://wordpress.org/plugins/recaptcha-jetpack/
 */

namespace coryhughart\recaptcha_jetpack_compat;

if ( ! defined( 'ABSPATH' ) ) exit; // Exit if accessed directly

function init() {
	if ( class_exists('Bozdoz_RJP_Plugin') ) {
		add_filter( 'the_content', __NAMESPACE__ . '\\add_gb_recaptcha', 1 );
		add_filter( 'widget_block_content', __NAMESPACE__ . '\\add_gb_recaptcha', 1 );
	}
}
add_action( 'init', __NAMESPACE__ . '\\init' );

function add_gb_recaptcha( $content ) {
	$form_close = "</div>\n<!-- /wp:jetpack/contact-form -->";

	if ( strpos( $content, $form_close ) === false ) return $content;

	if (get_option(\Bozdoz_RJP_Plugin::$prefix . 'recaptcha_type', 'v2') === 'invisible') {
		wp_enqueue_script(\Bozdoz_RJP_Plugin::$prefix . 'invisible_recaptcha_script');
	} else {
		wp_enqueue_script(\Bozdoz_RJP_Plugin::$prefix . 'recaptcha_script');
	}

	$content = str_replace( $form_close, '[' . \Bozdoz_RJP_Plugin::$prefix . '-button]' . $form_close, $content );

	return $content;
}