Hello,
I have not tested anything with 5.3 in a while, but I did do some iOS HandheldAR template testing today with what will eventually become 5.4 (currently very similar to UE5/Main) and looked into this problem a bit.
I think the collision tests are working for me, however with all of the options enabled on “Line Trace Tracked Objects” (Feature Points, Ground Plane, Plane Extents, Plane Boundary Polygon) I do get a confusing surplus of hits. If I just use the first hit I’ll usually get something closer to the camera than I wanted. In particular Feature Points are perhaps not terribly useful for application developers. They are the points ARKit uses to orient itself, and the documentation only says that they ‘usually’ are on real world object surfaces. After scanning around for a while I’m also ending up with multiple ground planes. That may be a bug, perhaps we need to throw away old ground planes when a new one is found? If I cut it down to only “Test Plane Boundary Polygon” I get more useful results: a hit on the seat of the chair, a hit on the floor below the chair. We sort the results in LineTraceTrackedObjects, so the first hit is the hit nearest the phone and therefore usually the desired hit.