Same problem Xcode 12.0.1 Catalina 10.15.7 Edit: it seems deactivating "Applications" in Spotlight fixes this issue. Should be confirmed by others If confirmed this is only a workaround and it must be fixed by Apple

As I wrote in my post (see below), I've unchecked Applications in Spotlight and I don't notice crashes of Spotlight anymore neither high CPU usage when Xcode simulator/previews is running. So it seems to be a workaround I've no solution for the Core Data with Simulator issue as I don't use it in my codes. Hope this helps

I've unchecked Applications in Spotlight because this is the location of the file (the Simulator) causing the crash and shown in the crash report. Are you sure is it the same root directory of the file (files ?) given in the report ?

Yes adding the /Users/<username>/Library/Developer/CoreSimulator/ path to the privacy tab in spotlight settings should be better than I made with unchecking the whole /Application in Spotlight. But Xcode brings too many other bugs as too high cpu usage in previews (even with this workaround and no spotlight crashs) or the print function which displays nothing in the debug output when in debug live preview. I've tried Xcode 12 beta 2 which even worse on cpu usage (on my Mac) and doesn't fix any of these bugs. So now I went back to Xcode 11.7 a most stable version I think.

Same issue Xcode 12.1 , macOS 10.15.7

when I try a live preview on my plugged iPad 6th generation Xcode returns an error. My iPad is in iPadOS 14.2 A click on the information icon next to the error message in Xcode shows another message telling Xcode is expecting an iPhone 12 device !

Same here with a lot of performance issues on previews Debug console for previews also have stopped to work with Xcode 12 (worked fine with Xcode 11) I develop on a MacBook Pro mi-2014 I’ve posted many questions/issues about Xcode 12 SwiftUI previews but no answer. I wonder if I need a paid account to get some answer through this forum So I’ve stopped to develop since I fed up with this release and to be ignored Good luck