Beta 3 of Xcode seems to fix this. I still received an error message but when compiling an app I was now able to manually select my Team ID.

FYI. When I try to do this on the Xcode beta it causes a crash. Crash log below for reference. Process: Xcode [1181] Path: /Applications/Xcode-beta.app/Contents/MacOS/Xcode Identifier: com.apple.dt.Xcode Version: 12.0 (17177.0.1) Build Info: UncleIDEFrameworks-17177000001000000~10 (12A8158a) Code Type: ARM-64 (Native) Parent Process: ??? [1] Responsible: Xcode [1181] User ID: 501 Date/Time: 2020-07-06 15:52:52.952 +0200 OS Version: Mac OS X 10.16 (20A5299w) Report Version: 12 Anonymous UUID: 2A97A021-1D40-BA56-4D66-99EBC1586852 Sleep/Wake UUID: 0B76EBD6-8353-496E-BBE2-5F107A1F96E3 Time Awake Since Boot: 3400 seconds Time Since Wake: 2600 seconds System Integrity Protection: enabled Crashed Thread: 10 Dispatch queue: ConcurrentQueue: -[IDEAccountDetailsRefresher start]blockinvoke2 Exception Type: EXCCRASH (SIGABRT) Exception Codes: 0x0000000000000000, 0x0000000000000000 Exception Note: EXCCORPSENOTIFY Application Specific Information: ProductBuildVersion: 12A8158a ASSERTION FAILURE in /Library/Caches/com.apple.xbs/Sources/UncleIDEFrameworks/UncleIDEFrameworks-17177.0.1/IDEFoundation/Provisioning/Provisioning Infrastructure/IDEProvisioningPortal.m:285 Details: A method claimed to have failed but provided no error! Object: <IDEProvisioningPortal: 0x15db0dfc0> Method: -listTeamsAndRolesWithAccount:error: Thread: <NSThread: 0x15da08e90>{number = 15, name = (null)} Open FDs: 42/7168 Hints: 0: Calling block provided by: 0 DVTDispatchAsync (in DVTFoundation) 1 -[IDEAccountDetailsRefresher start] (in IDEKit) 2 -[IDEAccountPrefsDeveloperAccountDetailViewController refreshUI] (in IDEKit) 3 -[IDEAccountPrefsDeveloperAccountDetailViewController setRepresentedObject:] (in IDEKit) 4 -[NSObject(NSKeyValueObservingPrivate) changeValueForKeys:count:maybeOldValuesDict:maybeNewValuesDict:usingBlock:] (in Foundation) 5 -[NSObject(NSKeyValueObservingPrivate) changeValueForKey:key:key:usingBlock:] (in Foundation) 6 NSSetObjectValueAndNotify (in Foundation) 7 -[IDEAccountPrefsPaneController updateReplacementView] (in IDEKit) 8 _47-[IDEAccountPrefsPaneController viewDidInstall]blockinvoke2 (in IDEKit) 9 DVTCALLINGCLIENTBLOCK (in DVTFoundation) 10 _DVTAsyncPerformBlockOnMainRunLoopblockinvoke (in DVTFoundation) 11 CFRUNLOOPISCALLINGOUTTOABLOCK (in CoreFoundation) 12 CFRunLoopDoBlocks (in CoreFoundation) 13 CFRunLoopRun (in CoreFoundation) 14 CFRunLoopRunSpecific (in CoreFoundation) 15 RunCurrentEventLoopInMode (in HIToolbox) 16 ReceiveNextEventCommon (in HIToolbox) 17 BlockUntilNextEventMatchingListInModeWithFilter (in HIToolbox) 18 DPSNextEvent (in AppKit) 19 -[NSApplication(NSEvent) nextEventMatchingEventMask:untilDate:inMode:dequeue:] (in AppKit) 20 -[DVTApplication nextEventMatchingMask:untilDate:inMode:dequeue:] (in DVTKit) 21 -[NSApplication run] (in AppKit) 22 NSApplicationMain (in AppKit) 23 start (in libdyld.dylib) Backtrace: 0 -[IDEAssertionHandler handleFailureInMethod:object:fileName:lineNumber:assertionSignature:messageFormat:arguments:] (in IDEKit) 1 DVTAssertionHandler (in DVTFoundation) 2 DVTAssertionFailureHandler (in DVTFoundation) 3 +[IDEProvisioningPortal errorForNoMatchingTeam:] (in IDEFoundation) 4 35-[IDEAccountDetailsRefresher start]blockinvoke3 (in IDEKit) 5 DVTCALLINGCLIENTBLOCK (in DVTFoundation) 6 DVTDispatchAsyncblockinvoke (in DVTFoundation) 7 dispatchcallblockandrelease (in libdispatch.dylib) 8 dispatchclientcallout (in libdispatch.dylib) 9 dispatchcontinuationpop (in libdispatch.dylib) 10 dispatchasyncredirectinvoke (in libdispatch.dylib) 11 dispatchrootqueuedrain (in libdispatch.dylib) 12 dispatchworkerthread2 (in libdispatch.dylib) 13 pthreadwqthread (in libsystempthread.dylib) 14 startwqthread (in libsystempthread.dylib) abort() called

I have the same issue on Big Sur (Xcode from App Store) running on the new Developer Transition Kit, which means I'm stuck before even starting to port my app.

Mine got approved & I will receive the kit today. I have a question about it: is there a way to run this mac purely with remote desktop / VNC? Ideally I want to stick this box on my network & remote into it for setup. I don't actually own a screen/keyboard/mouse to go with this Mac. Any suggestions?