FYI. Tested on Joomla 6.0.3 php 84.19 and had this backend error when trying to login Joomla backend:

Joomla\CMS\Application\SiteApplication::__construct(): Argument #1 ($input) must be of type ?Joomla\CMS\Input\Input, Joomla\Input\Input given, called in/libraries/src/Service/Provider/Application.php on line 101

in /libraries/src/Application/SiteApplication.php (line 86)

     *                                  application's client object, otherwise a default client object is created.
     * @param   ?Container  $container  Dependency injection container.
     *
     * @since   3.2
     */
    public function __construct(?Input $input = null, ?Registry $config = null, ?WebClient $client = null, ?Container $container = null)
    {
        // Register the application name
        $this->name = 'site';
        // Register the client ID

SiteApplication->__construct() in /libraries/src/Service/Provider/Application.php (line 101)
in /libraries/vendor/joomla/di/src/ContainerResource.php -> {closure:Joomla\CMS\Service\Provider\Application::register():100} (line 162)
in /libraries/vendor/joomla/di/src/Container.php -> getInstance (line 95)
Container->get() in /libraries/src/Service/Provider/Router.php (line 47)
in /libraries/vendor/joomla/di/src/ContainerResource.php -> {closure:Joomla\CMS\Service\Provider\Router::register():46} (line 162)
in /libraries/vendor/joomla/di/src/Container.php -> getInstance (line 95)
in /libraries/vendor/joomla/di/src/Container.php -> get (line 89)
Container->get() in /libraries/src/Extension/Service/Provider/MVCFactory.php (line 79)
in /libraries/vendor/joomla/di/src/ContainerResource.php -> {closure:Joomla\CMS\Extension\Service\Provider\MVCFactory::register():69} (line 168)
in /libraries/vendor/joomla/di/src/Container.php -> getInstance (line 95)
Container->get() in /libraries/src/Extension/Service/Provider/ComponentDispatcherFactory.php (line 63)
in /libraries/vendor/joomla/di/src/ContainerResource.php -> {closure:Joomla\CMS\Extension\Service\Provider\ComponentDispatcherFactory::register():62} (line 168)
in /libraries/vendor/joomla/di/src/Container.php -> getInstance (line 95)
Container->get() in /administrator/components/com_templates/services/provider.php (line 46)
in /libraries/vendor/joomla/di/src/ContainerResource.php -> {closure:Joomla\DI\ServiceProviderInterface@anonymous/administrator/components/com_templates/services/provider.php:28$1a::register():45} (line 168)
in /libraries/vendor/joomla/di/src/Container.php -> getInstance (line 95)
Container->get() in /libraries/src/Extension/ExtensionManagerTrait.php (line 177)
CMSApplication->loadExtension() in /libraries/src/Extension/ExtensionManagerTrait.php (line 51)
CMSApplication->bootComponent() in /libraries/src/Application/AdministratorApplication.php (line 253)
AdministratorApplication->getTemplate() in /libraries/src/Error/Renderer/HtmlRenderer.php (line 50)
HtmlRenderer->render() in /libraries/src/Exception/ExceptionHandler.php (line 142)
ExceptionHandler::render() in /libraries/src/Exception/ExceptionHandler.php (line 76)
ExceptionHandler::handleException() in /libraries/src/Application/CMSApplication.php (line 350)
CMSApplication->execute() in /administrator/includes/app.php (line 58)
require_once('/administrator/includes/app.php') in /administrator/index.php (line 32)

Did you actually test this yourself

Fatal error: Declaration of Joomla\CMS\Event\AbstractImmutableEvent::offsetSet($name, $value) must be compatible with Joomla\Event\Event::offsetSet($name, $value): void in D:\repos\j6\libraries\src\Event\AbstractImmutableEvent.php on line 65

@saisantosh-cpu Thank you very much for your contribution!

If you are creating a PR for the 5.4-dev branch, please make sure to test your changes against that branch rather than 6.0.3.

Additionally, the continuous integration currently reports PHP code style issues that need to be addressed.

We will set this PR to draft for now. Please feel free to update it within the next two weeks and mark it as ready for review again — otherwise, we may need to close it.