I'd start by confirming that diagnostics are enabled on that device, then use Xcode/Devices and Simulators/<name>/View Device Logs/This Device ...to confirm there are diagnostic log files present on the device.
You may want to be patient if Xcode indicates it is preparing that device for debugging...
However, after upgrading to the Catalina, iTunes was dead.
[syncing] iPhone via Finder could not copy diagnostic log files from iPhone to to Mac now.
That’s not my experience. Here’s what I did:
I created a small test project that, on tapping a button, calls
I ran that on my device using Xcode.
I stopped the app.
I disconnected my device from my Mac.
I ran the app from the Home screen.
I tapped the button and thus crashed the app.
I connected it to my Mac running 10.15.
In Finder, I selected my device on the left.
I clicked Sync.
After the sync was done I found the crash repor at the path
~/Library/Logs/CrashReporter/MobileDevice/Scout in a Can /CrashMe-2019-11-11-094201.crash. There’s a snippet below, just FYI.
Share and Enjoy
Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware
let myEmail = "eskimo" + "1" + "@apple.com"
Incident Identifier: 9F88DF5F-D421-4CBE-B4FD-9CBB00857E2F CrashReporter Key: dc6d7aa326dffab6fc564be7278a9ad639485ad0 Hardware Model: iPhone12,1 Process: CrashMe  Path: /private/var/containers/Bundle/Application/222714E9-C319-41A7-92E4-EF34DA296E8B/CrashMe.app/CrashMe Identifier: com.example.apple-samplecode.CrashMe Version: 1.0 (1.0) Code Type: ARM-64 (Native) Role: Foreground Parent Process: launchd  Coalition: com.example.apple-samplecode.CrashMe  Date/Time: 2019-11-11 09:42:00.8454 +0000 Launch Time: 2019-11-11 09:41:59.5589 +0000 OS Version: iPhone OS 13.2 (17B84) Release Type: User Baseband Version: 1.02.14 Report Version: 104 Exception Type: EXC_CRASH (SIGABRT) Exception Codes: 0x0000000000000000, 0x0000000000000000 Exception Note: EXC_CORPSE_NOTIFY Triggered by Thread: 0 Thread 0 name: Dispatch queue: com.apple.main-thread Thread 0 Crashed: …