Hey @dNovoNiels,
I got your example to work. 
What did I have to do?
1st: Your registered event in your DnovoEvents.php was wrong. There was an ‘s’ missing at the end of the string, since your controller is written with a ‘s’ at the end.
2nd: The path to your controller was missing a slash ( / ) at the beginning in the method onGetFrontendController. The path to your custom views directory was correct though and already included a slash.
3rd: Make sure to only use lower-case folder names in your views-folder. Had to change both “Frontend” and “events” to be lowercase.
After those three adjustments, the plugin worked for me and I could successfully call your custom controller with the proper template.
Do those information help you?
Patrick 