I'm trying to make a build on iOS platform but it fails the build with this message:
Vuforia Engine requires a minimum iOS version of 11.0. Please set the Target minimum iOS Version to 11.0 or above in the Player Settings.
I see that this has been a recent update since the update of Vuforia Engine version 8.1.7, but its still possible to build on Xcode side with the Deployment Target of 9.0 with no problems. You should probably limit this on the Xcode side too, just so it doesn't seem incoherent or causes bugs in the build on runtime.
Vuforia Engine 8.3.8
MacOS High Sierra 10.13.6