Turns out it was a problem with the nib file, which was not a problem for the "old way" of registering nibs. I recreated a new swift class + xib file and then it worked. Couldn't see what the difference was though...

Same problem here. I got 5 dev devices. All with iOS 18.0.1 dont get their symbols copied (stuck at various percentages, even after hours). iOS 17.x devices work without problems. macOS 15.0.1, Xcode 16.0. A real nasty problem! 15.0.1 didnt do it for me. Deleting DerivedData or iOS DeviceSupport doesnt help. Other solutions like putting device into flightmode and enforce usb doesnt help either...