First release of Yii Form Model package was done. It provides a base for form models and helps to fill, validate and display them.
For usage define a form model:
use Yiisoft\FormModel\Attribute\Safe;
use Yiisoft\FormModel\FormModel;
use Yiisoft\Validator\Rule\Email;
use Yiisoft\Validator\Rule\Length;
use Yiisoft\Validator\Rule\Required;

final class LoginForm extends FormModel
{
#[Label('Your login')]
#[Required]
#[Length(min: 4, max: 40, skipOnEmpty: true)]
#[Email(skipOnEmpty: true)]
private ?string $login = null;

#[Label('Your password')]
#[Required]
#[Length(min: 8, skipOnEmpty: true)]
private ?string $password = null;

#[Label('Remember me for 1 week')]
#[Safe]
private bool $rememberMe = false;
}

Fill it with data and validate using form hydrator:
use Psr\Http\Message\RequestInterface;
use Yiisoft\FormModel\FormHydrator;
use Yiisoft\FormModel\FormModel;

final class AuthController
{
public function login(RequestInterface $request, FormHydrator $formHydrator): ResponseInterface
{
$formModel = new LoginForm();
$errors = [];
if ($formHydrator->populateFromPostAndValidate($formModel, $request)) {
$errors = $formModel->getValidationResult()->getErrorMessagesIndexedByProperty();
}

// You can pass $formModel and $errors to the view now.
}
}

Display it using fields in the view:
use Yiisoft\FormModel\Field;
use Yiisoft\FormModel\FormModel;

echo Field::text($formModel, 'login');
echo Field::password($formModel, 'password');
echo Field::checkbox($formModel, 'rememberMe');

// ...