<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
<type name="MagentoFrameworkAppRouterNoRouteHandlerList">
    <arguments>
        <argument name="handlerClassesList" xsi:type="array">
            <item name="default" xsi:type="array">
                <item name="class" xsi:type="string">VendorModuleControllerNoRouteHandler</item>
                <item name="sortOrder" xsi:type="string">200</item>
            </item>
        </argument>
    </arguments>
</type>
</config>

<?php
namespace VendorModuleController;
class NoRouteHandler implements MagentoFrameworkAppRouterNoRouteHandlerInterface {

    protected $logger;
    public function __construct(PsrLogLoggerInterface $logger)
    {
        $this->logger = $logger;
    }

    public function process(MagentoFrameworkAppRequestInterface $request) {
        //log the 404 url
        $this->logger->info(':: 404 list ::'.$request->getPathInfo());
        $request -> setModuleName('cms') -> setControllerName('noroute') -> setActionName('index');
        return false;
    }

}