I just tried connecting some bluetooth joystick to my Android phone. I see my C2 game could register button presses responsively but it couldn't register any of D-Pad and the analog sticks. So it somehow got partial support by default.
Also, I tried on my smartphone and see that my bluetooth joystick could send signals to it. However, the gamepad testing site could not receive R3 analog stick, D-Pad, L2 and R2 button presses. It could receive L3 analog sticks fine though.
All these joystick charades on smartphone don't seem to get all the proper love, I feel... this is unfortunate.
But with Canvas+, can you try test and tell us the result, TecenGOD?