When the popover is presented (like Share sheet on any system app), then switch dark/light mode from the control center. The popover theme is unchanged unless you dismiss and present the popover again. I think the problem is that the popover view controller does not trigger the trait changed event. This problem has occurred since iOS 26 Beta 3. The previous version has no problem. On iOS 26.5 Beta 2 today, this problem is still.

Did you change something for the displayMode (toggle sidebar) button? I did nothing for that, and it can always be white correctly on dark mode in the Primary View.

Yes, I also see some dark mode color issues on context menu, textField/textView's edit menu. And the SplitViewController's primary view is the most serious. But they work fine on Apple's system built-in apps, like Safari, Photos, Mail, etc. So, I'm wondering whether it's a bug or is there something needs to be changed for iOS 26. It's already beta 4, and still have the color problem on basic component?

However and important, I can't use Any width, Compact height to match iPhone 14 Pro Max landscape.