We also have this issue with one customer account, it works with others.

I am seeing the same behaviour regarding the edit menu not showing: https://developer.apple.com/forums/thread/718677

Same here

Nevermind, renaming/deleting device_set.plist caused Xcode to recreate the simulators and I ended up with a lot of duplicated devices. Also, iOS 14 is again crashing and rebooting within the simulator :( Going to re-install everything again and not touch anything ...

I renamed the existing device_set.plist and started Xcode 11.5, later Xcode 12. This did not create any new file. However, after I rebooted macOS, I ended up with a new device_set.plist which looks like it only contains the simulators that I have in Xcode 11.5 and 12-beta1. The file is attached in the Feedback Assistant.

Ok, trying to remember all the steps: Deleted all existing Xcode versions from the Applications (Xcode 10.3, 11.4, 11.5, 12-beta1) sudo killall -9 com.apple.CoreSimulator.CoreSimulatorService Deleted the entire ~/Library/Developer folder Rebooted macOS Installed Xcode 12-beta1 and started the Fruta Sample to verify that iOS 14 simulators were working (mainly using iPhone 11 Pro simulator) -> success! Installed Xcode 11.5 and started one of my apps to verify iOS 13.5 simulators were working -> success Went to Xcode 11.5 -> Devices and Simulators and deleted a lot of simulators that I don't use, only keeping a few Used Xcode 12-beta1 again, started the Fruta sample with an iOS 14 simulator (iPhone 11 Pro) and it crashed again (+ reboot loop) Ran xcrun simctl diagnose, noticed that it was again complaining about a missing default simulator Looked at device_set.plist (inside ~/Library/Developer/CoreSimulator/Devices) and noticed a lot of simulators that I don't have any more (when running xcrun simctl list they don't show up, everything looks ok there) Edited device_set.plist to only include simulators that xcrun simctl list shows -> success, Xcode 12 simulators seem to be working again! After using Xcode 11.5 again, somehow device_set.plist gets modified again (without me adding & deleting any simulators) and again includes a lot of iOS 12.4 and older iOS 13 simulators. xcrun simctl list does not show those. However, so far, the iOS 14 simulators appear to be working fine.

Ok, didn't want to mark that as a solution ... somehow Xcode 11.5 messes up the device_set.plist and Xcode 12 is not happy with that.

It looks like something is odd with device_set.plist. After I deleted the simulators, they are still in that plist as "Default Devices". After I removed them from the plist manually, the Xcode 12 simulator seems to be running fine again.

After I deleted all installed Xcode versions and re-installed only Xcode 12-beta1 and Xcode 11.5, everything was working again. But after deleting some simulators from Xcode 11.5, the problem reappeared. I attached another diagnose to the FB issue.

Simulator.app itself did not crash, but rather iOS 14 inside. Even with no iOS app running (only starting Simulator.app with any iOS 14 device) it would end up in a crash & reboot loop. Looking at the diagnose file myself I noticed that there were a bunch of missing simulators. So I uninstalled all Xcode versions (10.3, 11.4, 11.5 and 12.0-beta1), deleted ~/Library/Developer and re-installed Xcode 11.5 and 12.0-beta1. Everything seems to be working fine now!

Thank you for looking into this. The issue is FB7756203 and I just attached the output of the diagnose tool.