I've updated test device to iOS 26.1 (23B5059e) and it looks like topColumnForCollapsingToProposedTopColumn isn't being called.
The code has been fine up until iOS 26.1. Is that a UIKit issue or shall I find another way to get my splitview to show the primary view as default?
This is unexpected. Please may you file a feedback report with a sample project exhibiting this issue.
I think this is an issue with my app.
If I set .delegate before setting .preferredDisplayMode and .preferredSplitBehavior then topColumnForCollapsingToProposedTopColumn gets called.
My app had it the other way around so it was properly just luck that I didn't see an issue on older iOS versions.
