Analog joystick axes can only be used with Python (or logic nodes).
But there is an extra problem with Controllers other than Gamepads.
UPBGE makes usage of a file called gamecontrollerdb.txt created by an online community which only allows gamepads and no Flightsticks or other USB-Controllers.
So to use a Flightstick you must edit this file located in the directory datafiles/gamecontroller.
There you can add your own configuration.
To create a configuration you must use some external tools.
This is all quite fiddly you see.
But I managed to get my Microsoft Sidewinder ForceFeedback 2 Joystick working and also a virtual Joystick for HeadTracking.
Some more infos here: