The issue seems to be the .toolbarBackground modifier, not the Map itself. I see the same problem when using a MKMapView, as long as I add that modifier.
However, as you correctly described, Map will underlap the navigation bar by default and thus requires the .toolbarBackground modifier to achieve the desired look.
Sadly I couldn't yet find a solution for customizing the back button appearance (which, to my knowledge, isn't possible without resorting to UIKit and appearance proxies) while using .toolbarBackground. Any pointers are much appreciated!
Topic:
UI Frameworks
SubTopic:
SwiftUI
Tags: