Update: It is possible to map a controller for the game on andorid
Not sure if mods or any higher up want to pin this for anyone else who want to do this in the future
To do this is easy, follow my steps below.
(I'm using PS4 Controller, works for XBOX Controller also)
Step 1: go to Joiplay - click the 3 dots - settings - then click P.Essential Settings - then turn Input Override ON then SAVE (dont forget to save or it won't work)
Step 2: go into game - click dropdown list at the top of screen - click settings - scroll down till you see gamepad mapping - click it and remove all.
Step 3: press button on controller, best way to do this is to follow the amount ingame controls needed (in this case is which 12)
Step 4 (hardest step): after selecting your 12 button manually connect them to the ingame buttons (image) to the button u want on controller - Eg. USE KEY ITEMS is button D but you want that to be R2 - so select the R2 mapping bind then click on the 0 in the middle and change that to D and that will make it so that when u press R2 you open the KEY ITEMS menu. (Do the rest for the other bind)
That it - that's your controller connected to joiplay and Pokemon infinite fusion game have fun 👍.
If mods want me to make a full guide on this with proper screenshot please let me know I'll be happy to help the community.