i am aware that UE4 does not support MFI gamepads on iOS but i have installed a plugin that has been very kindly created and posted on github by Ketlius https://github.com/EpicGames/UnrealEngine/pull/2014
the plugin enables the use of MFI controllers on iOS. it does not work in the editor ( i use a Xbox 360 controller to test and program )
When launched or packed on the device the MFI controller Steel Series Nimbus works great in the game.
The problem is in the menu screen. when focus us used in UMG using the DPad to navigate the button selection is erratic and tends to pull selection to the buttons nearest the centre of the screen the select (A) button is intermittent and it also interferes with touch input.