See also How to hide the home indicator with SwiftUI? on Stack Overflow and the accompanying gist. The complexity of this solution underscores willt42's comment.
I would greatly appreciate a view modifier like:
.homeIndicator(hidden: true)
// or
.prefersHomeIndicatorAutoHidden(true)
// similar to
.statusbar(hidden: true)
// or
navigationBarHidden(true)
statusbar(hidden:)
navigationBarHidden(_:)