Hey! Sorry -- we should've made this clearer. ARKit only works on devices running iOS 11, and some particular devices at that:
iPhone 6s and 6s Plus, iPhone 7 and 7 Plus, iPhone SE, iPad Pro (9.7, 10.5 or 12.9) – both first-gen and 2nd-gen, iPad (2017), iPhone 8 and 8 Plus, iPhone X
I think these are the ones, at the time of posting this comment.