This seems to have been fixed in iPadOS 26.1 Beta 2.

I have the same issue, I'm not able to reach the same side bar appearance as the Settings app with UISplitViewController (tested on iOS 26 Beta 4). I've created a very basic "double column" split view controller and there isn't the Liquid Glass effect around the edges of the primary view controller. Interestingly, it does work if one uses the SwiftUI equivalent NavigationSplitView. So either it's a bug in UISplitViewController, or it's not planned for it to support that appearance (hopefully not!).

We have the same issue, and it's very annoying. We rely on Universal Links for login (for secure callback from ASWebAuthenticationSession to the app), so App Review definitely stumble upon that issue during review. We never get any user tickets about it and it never occurs during our own testing, but it happens pretty often during App Review. So far, luckily, we have explained the situation to App Review, they try again, and it works. But it feels very fragile; there must be something with the App Review install process which is not reliably registering Universal Links.

Same here on iOS 17 beta 6 (real device only, works fine in the Simulator).

iOS 15.5 RC is out, and the problem is still there. This is a big issue for us. Basically, it seems that ASWebAuthenticationSession and SFSafariViewController no longer detect associated domains URLs if those are triggered by a redirection.

The issue seems to unrelated to iOS 15.5, but due to a recent change in our backend which made us lost our domain registration (the apple-app-site-association verification was failing due to a redirect, which is forbidden). It was just a coincidence that our first device that dropped the association was the one running iOS 15.5.