Controller or its method is not found: \App\Controllers\Tasks::index

It is because of security enhancement since v4.2.

Since v4.2, Auto Routing is disabled by default.
So you need to define all routes in Routes.php.

If you set $routes->setAutoRoute(true), Auto Routing (Legacy) will be enabled.
But we do not recommend to use Auto Routing (Legacy), because it has too much security risks.

If you want to use Auto Routing (you don't want to add all routes in Routes.php),
we recommend to use new Auto Routing (Improved).
https://codeigniter4.github.io/CodeIgnit...to-routing

ci-phpunit-test | CodeIgniter Testing Guide | CodeIgniter 3 to 4 Upgrade Helper

@kenjis very impressive, guidance with kindness 
thank you for struggle to help us learning CodeIgniter.
regards

Newbie here in CodeIgniter World !! Please appologize if any nonsense from me.  

environment: Windows 10, XAMPP 3.3.0, VS Code, SQLyog Community Ed.