I have a really simple test. I exported an area around my office as a MMPK file using ArcGIS Pro. I've tried a few different basemap layers, they all work the same. The MMPK loads and is displayed in my MapView swift test project, no problem. I am reading my current GPS coordinates and plotting the points to the GraphicsOverlay assigned to the MapView, but the points end up miles away from MMPK area. If I use Map( basemapStyle: .arcGISTopographic ), instead of loading the MMPK, then the GPS points are displaying on the map where they should.
I'm guessing there's some kind of coordinate system issue between the MMPK and the GPS coordinate space (wgs84), but everything looks like it's in the same coordinate space. Any ideas what's going wrong or how best to debug it?