How to enable debug toolbar in CI4.0.0-rc.3

Hello ! Yes, that is exactly what I am talking about. I had this thread in mind too.
It doesn't matter where you CI is placed on the server, it is the final url which is important. And, in your previous messages you said "www.domain.com/projects/CI4/".
What's happening if you add "?debugbar" to your url ? Ex: http://localhost:8080/?debugbar

PS: The port is not important. I just wanted you to use "php spark" and CI's default settings, in order to have the "standard" configuration, and be sure this is not coming from your custom settings.