Through this tutorial, I learned about wikitude.
I built it with Samsung Galaxy S7 and S8, but I got the same error as the picture above. It also installed the Google AR CORE SDK. I don't know why.
Since SDK 7.2, we have integrated ARCore and ARKit within our platform. So this message tells you that, because the phone you are using supports ARCore, you are using Instant Tracking provided by Wikitude SDK with the functionalities of ARCore. You just need to move around a bit with your phone until you find a good scene and the target turns green.