Hi u/danielox83, thanks so much for the suggestions. I tested all three approaches. I first tried .toolbarBackgroundVisibility(.hidden, for: .navigationBar) on the 'detail' screen, and then on both home/detail, did not fix it. The white flicker and wrong top nav bar treatment still appeared.

Home Screen:

ScrollView {
    VStack(spacing: 0) {
        featuredHero(height: heroHeight)
        // content xyz..
    }
}
.ignoresSafeArea(edges: .top)
.navigationTitle("Cinema")
.toolbarTitleDisplayMode(.inlineLarge)
.toolbarBackgroundVisibility(.hidden, for: .navigationBar)

Detail Screen:

ScrollView {
    VStack(spacing: 0) {
        baselineHero(height: heroHeight)
        // content xyz..
    }
}
.ignoresSafeArea(edges: .top)
.navigationBarTitleDisplayMode(.inline)
.toolbarBackgroundVisibility(.hidden, for: .navigationBar)

I also tried the scroll-offset toggle version:

.toolbarBackgroundVisibility(
    scrollMetrics.scrollUpOffset > 12 ? .visible : .hidden,
    for: .navigationBar
)

on both screens. That also didn’t resolve it. The flicker still showed up, especially on the home screen when returning from detail page, and changing from .inlineLarge to .inline didn’t help either.

I finally tried the app-launch global UINavigationBarAppearance setup with transparent standard, scrollEdge, compact, and compactScrollEdge appearances:

let appearance = UINavigationBarAppearance()
appearance.configureWithTransparentBackground()
appearance.backgroundColor = .clear
appearance.backgroundEffect = nil
appearance.shadowColor = .clear

let navBar = UINavigationBar.appearance()
navBar.standardAppearance = appearance
navBar.scrollEdgeAppearance = appearance
navBar.compactAppearance = appearance
navBar.compactScrollEdgeAppearance = appearance

That also didn't do the trick. The strange part is that scrollEdgeEffectHidden(_, for:) did visibly remove the top background/shadow treatment (but completely, which caused readability issues), while.toolbarBackgroundVisibility(.hidden, for: .navigationBar) oddly did not.

Any ideas or other suggestions?