const [form] = Form.useForm();

  const [buttonDisabled, setButtonDisabled] = useState(true);

  return (

    <Modal

      ...

      okButtonProps={{ disabled:  buttonDisabled  }}

    >

     <Form

        form={form}

        ...

        onFieldsChange={() =>

          setButtonDisabled(

            form.getFieldsError().some((field) => field.errors.length > 0)

          )

        }

      >