I know this post is super old, but wanted to mention I spent a fair bit of time dealing with this issue myself. I did actually design a UMG virtual keyboard, and it is currently pending review in the marketplace!
It was honestly not too too difficult to make, but if anyone wants a quick plug and play solution, my keyboard should work for any platform and it’s just 1 step to implement! 
Keep an eye out for ‘Easiest Keyboard For Gamepad’ on the store in the next couple weeks.
