Ok so thanks go to jackal27!
Original thread : https://boards.dingoonity.org/gpd-android-devices/your-multiplayer-controller-solution-(issues-w-mayflash-gamecube-adapter)/
So I bought this controller a while back for my 4yo son, so he can play some emus on his tablet.
Then later on jackal27 had mentioned that a dongle could make it work for the gpd xd. So I bought it and tried it out.
I highly recommend this dongle to everyone that either connects their gpd to tv to play, or just need multicontroller support.
The tiny 8bitdo controller worked perfectly with the gpd xd. But I was curious as to all of the controllers it supported. So I had some ps3 controllers I wanted to try out. THEY WORKED!
So the one downside is that you need one dongle per controller, but the benefits are crazy. Not to mention it is only 13 USD : https://www.amazon.com/gp/product/B076B995TL
So if you have: ps3,
and want to use them on your gpd xd, just get this dongle!
I have tested that lil 8BitDo controller and ps3, so those are verified by me. I don't see any problems connecting the other controllers.