This feature was presented in iOS 18 and got broken in iOS 18.3, we are on 26.4 Beta 4 now. This is crazy that we have a completely broken feature for more than one major release ... I have code for this feature commented out for more than a year waiting to be uncommented one day.

No, it's not fixed, iOS 26.2 Beta 3, still the same issue, most of file formats cannot generate thumbnails with QLThumbnailGenerator + it usually give 1 of 2 versions of icon for the same file RANDOMLY, and UIDocumentInteractionController(url: fileURL).icons returns blank icons starting from 18.3