Does the handbrake show up in windows control panel?
Press Start and type "game controller" and start the "setup usb game controllers" app.
(As far as I understand it is normal to see two DD2 devices as stated above)
The handbrake might be named "USB Gamepad" or possibly "Heusinkveld sim Handbrake".
Select it and click Properties, there you can test it, and confirm which device responds to you handbraking. You can also calibrate it, so that it performs a correct 0-100% range detection. Calibration might be the reason none of the axes responds in LFS. Once done click OK.
Start LFS and go to the Axes screen, does any of the axes respond to you pulling the handbrake?
Also, do NOT click the Handbrake-device in LFS, I think that is used for selecting the Wheel-device, so click the Wheel-device once, and leave it there, otherwise that will reset your input config!
But then you can continue assign buttons and axes for ALL connected devices.
Pressing pedals, yanking handkrake, and turning the wheel, will move the corresponding asxi/slider, then you will see which axis to assign to which function.