ArcRotateCameraGamepadInput ignores the element parameter in attachControl
ArcRotateCameraKeyboardMoveInput ignores the element parameter in attachControl
ArcRotateCameraMouseWheelInput ignores the element parameter in attachControl
Yep, seems like the element is mainly ignored here.
Most of those events are global events (window/document events). What is the exact use case you have that you need to change the element per input type?
I would like to make controls work even when the canvas does not have focus.
I have found out that this works nicely doing:
engine.inputElement = document.getElementsByTagName(“body”)[0];
But the code and the documentation is very misleading
Yep, this is the way to go 
The camera attach and detach control actually don’t require the HTML element actually, this was changed a long time ago. We’ll remove it till the next release. Thanks for reporting!