Same issue here. Filed as FB23807146 with traces, DTServiceHub crash reports, and a sysdiagnose attached. I reproduced on iPadOS 26.5.2 and the iOS 27.0 public beta, with both Xcode 26.6 and 27.0 beta, from the GUI or xctrace, and always stopping gracefully with the app frontmost. A Time Profiler-only recording of the same app works fine. The device logs show a likely culprit for why the trace is empty: swiftuitraced never launches (launchd: failed lookup: name = com.apple.swiftuitracingsupport.xpc … No such process), and when the recording stops DTServiceHub hits "SwiftUITracingSupport/IPC.swift:548: Fatal error: swiftuitraced likely crashed. state is none" and dies while draining the ktrace session, so no data ever reaches the host. One DTServiceHub crash report per recording attempt.