Create a standalone zend-inputfilter with a ContainerInterop container.

zend-inputfilter-servicemanager.php

<?php

require 'vendor/autoload.php';

use Xtreamwayz\HTMLFormValidator\Validator\RecaptchaValidator;
use Zend\Filter\FilterPluginManager;
use Zend\InputFilter\Factory;
use Zend\InputFilter\InputFilterPluginManager;
use Zend\ServiceManager\Config;
use Zend\ServiceManager\ServiceManager;
use Zend\Validator\ValidatorPluginManager;

$config = [
    'zend-inputfilter' => [
        'validators' => [
            // Attach custom validators or override standard validators
            'invokables' => [
                'recaptcha' => RecaptchaValidator::class,
            ],
        ],
        'filters'    => [
            // Attach custom filters or override standard filters
            'invokables' => [
            ],
        ],
    ],
];

// Build container
$container = new ServiceManager($config);
$container->setService('config', $config);

// Build factory
$factory = new Factory(
    new InputFilterPluginManager($container)
);
$factory->getDefaultFilterChain()->setPluginManager(
    new FilterPluginManager($container, $config['zend-inputfilter']['filters'])
);
$factory->getDefaultValidatorChain()->setPluginManager(
    new ValidatorPluginManager($container, $config['zend-inputfilter']['validators'])
);

//$factory = new Factory();

$input = $factory->createInput(['name' => 'foo']);
$input->getFilterChain()
      ->attachByName('stringtrim')
      ->attachByName('alpha');
//$input->getValidatorChain()->attachByName('recaptcha', ['key' => 'secret_key']);

$inputFilter = $factory->createInputFilter([]);
$inputFilter->add($input);
$inputFilter->setData([
    'foo' => ' Bar3 ',
]);

var_dump($factory->getDefaultValidatorChain()->getPluginManager()->has('recaptcha'));
var_dump($input->getValidatorChain()->getPluginManager()->has('recaptcha'));
var_dump($inputFilter->isValid());
var_dump($inputFilter->getValues());