Xcode 12 Beta 4, long time for Debug launch on iOS 14 b4

Look at the console output. My guess is that you will see message like this pop up about 1 every 3-4 seconds. That is what is causing the long load times. It doesn't happen on a real device, but only on the simulators for iOS 13 & 14.

2020-08-09 20:53:24.798020-0400 HS4[19985:1381381] libMobileGestalt MobileGestaltCache.c:38: No persisted cache on this platform.
2020-08-09 20:53:30.748666-0400 HS4[19985:1380170] HALCADClient::ConnectToServer: failed to find the AHS sub-server port, Error: 0x10004003
2020-08-09 20:53:35.749000-0400 HS4[19985:1380170] HALCADClient::ConnectToServer: failed to find the AHS sub-server port, Error: 0x10004003
2020-08-09 20:53:35.749352-0400 HS4[19985:1380170] HALDefaultDevice::Initialize: couldn't add the default input device listener, Error: 268451843 (\^P)
2020-08-09 20:53:40.750540-0400 HS4[19985:1380170] HALCADClient::ConnectToServer: failed to find the AHS sub-server port, Error: 0x10004003
2020-08-09 20:53:40.750906-0400 HS4[19985:1380170] HALDefaultDevice::Initialize: couldn't add the default output device listener, Error: 268451843 (\^P)
2020-08-09 20:53:45.752149-0400 HS4[19985:1380170] HALCADClient::ConnectToServer: failed to find the AHS sub-server port, Error: 0x10004003
2020-08-09 20:53:45.752563-0400 HS4[19985:1380170] HALDefaultDevice::Initialize: couldn't add the default system output device listener, Error: 268451843 (\^P)
2020-08-09 20:53:50.753751-0400 HS4[19985:1380170] HALCADClient::ConnectToServer: failed to find the AHS sub-server port, Error: 0x10004003
2020-08-09 20:53:50.753981-0400 HS4[19985:1380170] HALDefaultDevice::Initialize: couldn't add the default shared output device listener, Error: 268451843 (\^P)
2020-08-09 20:53:50.754989-0400 HS4[19985:1380170] [plugin] AddInstanceForFactory: No factory registered for id <CFUUID 0x600003634e60> F8BB1C28-BAE8-11D6-9C31-00039315CD46
2020-08-09 20:53:50.756684-0400 HS4[19985:1380170] Error loading /Library/Audio/Plug-Ins/HAL/BartenderAudioPlugIn.plugin/Contents/MacOS/BartenderAudioPlugIn: dlopen(/Library/Audio/Plug-Ins/HAL/BartenderAudioPlugIn.plugin/Contents/MacOS/BartenderAudioPlugIn, 262): no suitable image found. Did find:
/Library/Audio/Plug-Ins/HAL/BartenderAudioPlugIn.plugin/Contents/MacOS/BartenderAudioPlugIn: mach-o, but not built for platform iOS-sim
2020-08-09 20:53:50.756915-0400 HS4[19985:1380170] [plugin] Cannot find function pointer NewSHPPlugIn for factory <CFUUID 0x600003634500> 834FC054-C1CC-11D6-BD01-00039315CD46 in CFBundle/CFPlugIn 0x7fa565019c70 </Library/Audio/Plug-Ins/HAL/BartenderAudioPlugIn.plugin> (bundle, not loaded)
2020-08-09 20:53:50.757190-0400 HS4[19985:1380170] AudioObjectSetPropertyData: no object with given ID 0
2020-08-09 20:53:50.757379-0400 HS4[19985:1380170] 83: Failed to set processVolumeScalar on device. Error: 560947818
2020-08-09 20:53:55.924562-0400 HS4[19985:1382805] HALCADClient::ConnectToServer: failed to find the AHS sub-server port, Error: 0x10004003
2020-08-09 20:53:55.925082-0400 HS4[19985:1382805] HALCADClient::GetPropertyData: unknown property
2020-08-09 20:53:55.925347-0400 HS4[19985:1382805] [ddagg] AggregateDevice.mm:800 couldn't get default input device, ID = 0, err = 0!
2020-08-09 20:54:00.927012-0400 HS4[19985:1382805] HALCADClient::ConnectToServer: failed to find the AHS sub-server port, Error: 0x10004003
2020-08-09 20:54:00.927255-0400 HS4[19985:1382805] HALCADClient::GetPropertyData: unknown property
2020-08-09 20:54:00.927365-0400 HS4[19985:1382805] [ddagg] AggregateDevice.mm:800 couldn't get default output device, ID = 0, err = 0!
2020-08-09 20:54:00.927567-0400 HS4[19985:1382805] [aqme] 352: error -66680 finding/initializing Device.AQDefaultDevice
2020-08-09 20:54:00.927709-0400 HS4[19985:1382805] 111: * * * NULL AQIONode object
2020-08-09 20:54:00.927757-0400 HS4[19985:1380170] [aqme] 352: error -66680 finding/initializing Device.AQDefaultDevice
2020-08-09 20:54:00.927858-0400 HS4[19985:1382805] 848: Can't make UISound Renderer
2020-08-09 20:54:00.927847-0400 HS4[19985:1380170] [AQ] 1899: failed (-66680); will stop (12000/0 frames)
2020-08-09 20:54:00.928927-0400 HS4[19985:1380170] AudioDeviceStop: no device with given ID
2020-08-09 20:54:00.929094-0400 HS4[19985:1380170] [aqme] 352: error -66680 finding/initializing Device.AQDefaultDevice
2020-08-09 20:54:00.929225-0400 HS4[19985:1380170] [AQ] 1899: failed (-66680); will stop (12000/0 frames)
2020-08-09 20:54:00.997159-0400 HS4[19985:1382805] [] nwprotocolgetquicimageblockinvoke dlopen libquic failed

I have this same thing happening on real hardware only. Even happening after creating a new "Hello World" project.

I fixed this for my situation by deleting the contents of ~/Library/Developer/Xcode/iOS DeviceSupport/.

I have the same problem here and now with Xcode 12 GM!

When launching a debug session on a device it takes more than 75 seconds until the UI appears on the device.

Clearing ~/Library/Developer/Xcode/iOS DeviceSupport/ does help indeed!

I will try to keep in mind: beside clearing out DerivedData it may also be helpful to clear the content of iOS DeviceSupport.

Is this a broken system?

Same problem here with Xcode 12 GM, iPhone X, iPhone SE 2nd generation, iPhone XR ... taking long time to start debug session on real devices ...annoying!!! Apple, solve this please!!