Background: I've used Xcode 11.3 for years with my 2015 macbook pro running OS 10.14.6. About a week ago, I thought I had to solve a problem by updating OS. Under that OS, 12.x, I installed the newest Xcode. This ended up not being the right solution, and caused other issues, so I switched back to 10.14.6. After the switch-back, I had to also delete that newer Xcode, and re-download Xcode 11.3. Now, it will not open at all, and I get a popup that says Loading a plug-in failed The plug-in or one of its prerequisite plug-ins may be missing or damaged and may need to be reinstalled. I try opening via Terminal and this is the printout: $ /Applications/Xcode.app/Contents/MacOS/Xcode ; exit; then some warnings that I suspect are not the problem, then the errors: 2022-11-12 19:58:27.335 Xcode[1562:20866] [MT] DVTPlugInLoading: Failed to load code for plug-in com.apple.dt.dbg.DebuggerFoundation (/Applications/Xcode.app/Contents/PlugIns/DebuggerFoundation.ideplugin), error = Error Domain=NSCocoaErrorDomain Code=3588 "dlopen(/Applications/Xcode.app/Contents/PlugIns/DebuggerFoundation.ideplugin/Contents/MacOS/DebuggerFoundation, 265): Symbol not found: OBJC_CLASS$_NSConstantIntegerNumber Referenced from: /Library/Developer/PrivateFrameworks/CoreSimulator.framework/Versions/A/Frameworks/CoreSimulatorUtilities.framework/Versions/A/CoreSimulatorUtilities (which was built for Mac OS X 11.0) Expected in: /System/Library/Frameworks/Foundation.framework/Versions/C/Foundation in /Library/Developer/PrivateFrameworks/CoreSimulator.framework/Versions/A/Frameworks/CoreSimulatorUtilities.framework/Versions/A/CoreSimulatorUtilities" UserInfo={NSLocalizedFailureReason=The bundle couldn’t be loaded., NSLocalizedRecoverySuggestion=Try reinstalling the bundle., NSFilePath=/Applications/Xcode.app/Contents/PlugIns/DebuggerFoundation.ideplugin/Contents/MacOS/DebuggerFoundation, NSDebugDescription=dlopen(/Applications/Xcode.app/Contents/PlugIns/DebuggerFoundation.ideplugin/Contents/MacOS/DebuggerFoundation, 265): Symbol not found: OBJC_CLASS$_NSConstantIntegerNumber Referenced from: /Library/Developer/PrivateFrameworks/CoreSimulator.framework/Versions/A/Frameworks/CoreSimulatorUtilities.framework/Versions/A/CoreSimulatorUtilities (which was built for Mac OS X 11.0) Expected in: /System/Library/Frameworks/Foundation.framework/Versions/C/Foundation in /Library/Developer/PrivateFrameworks/CoreSimulator.framework/Versions/A/Frameworks/CoreSimulatorUtilities.framework/Versions/A/CoreSimulatorUtilities, NSBundlePath=/Applications/Xcode.app/Contents/PlugIns/DebuggerFoundation.ideplugin, NSLocalizedDescription=The bundle “DebuggerFoundation” couldn’t be loaded.}, dyldError = dlopen(/Applications/Xcode.app/Contents/PlugIns/DebuggerFoundation.ideplugin/Contents/MacOS/DebuggerFoundation, 0): Symbol not found: OBJC_CLASS$_NSConstantIntegerNumber Referenced from: /Library/Developer/PrivateFrameworks/CoreSimulator.framework/Versions/A/Frameworks/CoreSimulatorUtilities.framework/Versions/A/CoreSimulatorUtilities (which was built for Mac OS X 11.0) Expected in: /System/Library/Frameworks/Foundation.framework/Versions/C/Foundation in /Library/Developer/PrivateFrameworks/CoreSimulator.framework/Versions/A/Frameworks/CoreSimulatorUtilities.framework/Versions/A/CoreSimulatorUtilities 2022-11-12 19:58:27.336 Xcode[1562:20866] [MT] DVTAssertions: Warning in /Library/Caches/com.apple.xbs/Sources/IDEFrameworks/IDEFrameworks-15715/IDEFoundation/Initialization/IDEInitialization.m:305 Details: Xcode failed its initial plug-in scan, error = Error Domain=DVTPlugInErrorDomain Code=2 "Loading a plug-in failed." UserInfo={DVTPlugInIdentifierErrorKey=com.apple.dt.dbg.DebuggerFoundation, DVTPlugInExecutablePathErrorKey=/Applications/Xcode.app/Contents/PlugIns/DebuggerFoundation.ideplugin/Contents/MacOS/DebuggerFoundation, NSLocalizedRecoverySuggestion=The plug-in or one of its prerequisite plug-ins may be missing or damaged and may need to be reinstalled., DVTPlugInDYLDErrorMessageErrorKey=dlopen(/Applications/Xcode.app/Contents/PlugIns/DebuggerFoundation.ideplugin/Contents/MacOS/DebuggerFoundation, 0): Symbol not found: OBJC_CLASS$_NSConstantIntegerNumber Referenced from: /Library/Developer/PrivateFrameworks/CoreSimulator.framework/Versions/A/Frameworks/CoreSimulatorUtilities.framework/Versions/A/CoreSimulatorUtilities (which was built for Mac OS X 11.0) Expected in: /System/Library/Frameworks/Foundation.framework/Versions/C/Foundation in /Library/Developer/PrivateFrameworks/CoreSimulator.framework/Versions/A/Frameworks/CoreSimulatorUtilities.framework/Versions/A/CoreSimulatorUtilities, NSLocalizedDescription=Loading a plug-in failed., NSFilePath=/Applications/Xcode.app/Contents/PlugIns/DebuggerFoundation.ideplugin, NSLocalizedFailureReason=The plug-in “com.apple.dt.dbg.DebuggerFoundation” at path “/Applications/Xcode.app/Contents/PlugIns/DebuggerFoundation.ideplugin” could not be loaded. The plug-in or one of its prerequisite plug-ins may be missing or damaged., NSUnderlyingError=0x7f9d0b617cf0 {Error Domain=NSCocoaErrorDomain Code=3588 "dlopen(/Applications/Xcode.app/Contents/PlugIns/DebuggerFoundation.ideplugin/Contents/MacOS/DebuggerFoundation, 265): Symbol not found: OBJC_CLASS$_NSConstantIntegerNumber Referenced from: /Library/Developer/PrivateFrameworks/CoreSimulator.framework/Versions/A/Frameworks/CoreSimulatorUtilities.framework/Versions/A/CoreSimulatorUtilities (which was built for Mac OS X 11.0) Expected in: /System/Library/Frameworks/Foundation.framework/Versions/C/Foundation in /Library/Developer/PrivateFrameworks/CoreSimulator.framework/Versions/A/Frameworks/CoreSimulatorUtilities.framework/Versions/A/CoreSimulatorUtilities" UserInfo={NSLocalizedFailureReason=The bundle couldn’t be loaded., NSLocalizedRecoverySuggestion=Try reinstalling the bundle., NSFilePath=/Applications/Xcode.app/Contents/PlugIns/DebuggerFoundation.ideplugin/Contents/MacOS/DebuggerFoundation, NSDebugDescription=dlopen(/Applications/Xcode.app/Contents/PlugIns/DebuggerFoundation.ideplugin/Contents/MacOS/DebuggerFoundation, 265): Symbol not found: OBJC_CLASS$_NSConstantIntegerNumber Referenced from: /Library/Developer/PrivateFrameworks/CoreSimulator.framework/Versions/A/Frameworks/CoreSimulatorUtilities.framework/Versions/A/CoreSimulatorUtilities (which was built for Mac OS X 11.0) Expected in: /System/Library/Frameworks/Foundation.framework/Versions/C/Foundation in /Library/Developer/PrivateFrameworks/CoreSimulator.framework/Versions/A/Frameworks/CoreSimulatorUtilities.framework/Versions/A/CoreSimulatorUtilities, NSBundlePath=/Applications/Xcode.app/Contents/PlugIns/DebuggerFoundation.ideplugin, NSLocalizedDescription=The bundle “DebuggerFoundation” couldn’t be loaded.}}} Function: BOOL _IDEInitializePlugInManager(IDEInitializationOptions, NSError *__autoreleasing *) Thread: <NSThread: 0x7f9d08505aa0>{number = 1, name = main}