Just wrote the following controller:

    namespace MySite\MyCustomModule\Controller\Dashboard;
    
    use Magento\Customer\Controller\AccountInterface;
    use Magento\Framework\App\Action\HttpGetActionInterface as HttpGetActionInterface;
    use Magento\Framework\View\Result\PageFactory;
    
    class Index implements AccountInterface, HttpGetActionInterface
    {
        /**
         * @var PageFactory
         */
        protected $resultPageFactory;
    
        /**
         * @param PageFactory $resultPageFactory
         */
        public function __construct(
            PageFactory $resultPageFactory
        ) {
            $this->resultPageFactory = $resultPageFactory;
        }
    
        /**
         * Default customer account page
         *
         * @return \Magento\Framework\View\Result\Page
         */
        public function execute()
        {
        
            return $this->resultPageFactory->create();
        }
    }


However, when trying to get results, 

also di.xml

router id="standard"
    route id="customer"
        module name="MySite_MyCustomModule" after="Magento_Customer"
    route
router

go to the needed route http://mysite.lo/customer/dashboard and get the following issue:

1 exception(s):
Exception #0 (InvalidArgumentException): Invalid return type

Exception #0 (InvalidArgumentException): Invalid return type
<pre>#1 Magento\Framework\App\Bootstrap->run() called at [pub/index.php:31]
</pre>


and even debug cannot log in to method **execute**.

Does anyone face this issue?