My bad, after submitting the question I realized I had set the boundarySupplementaryItems property on the entire layout instead of on the sections...

I have the same question/comment.

I watched the SwiftUI Accessibility: Beyond the Basics session and like what I saw, but it did not address my question regarding support for LargeContentViewer on custom views. I have a scenario in one of the apps I am working on - actually trying to decide to do the whole thing in SwiftUI or stick with UIKit for now - that requires some views that cannot change size. Am going through a checklist of components and accessibility features that I feel are must have to aid in my SwiftUI vs UIKit decision.

Actually the hack that uses KVO does not work with iOS 14. The fonts just get changed to something weird, definitely not what you were trying to set.