Just to be clear: Does it really mean, that we can never create a KEXT anymore with XCode above 9.4.1?(I did run in the same problem with an audio KEXT, "vtable out of date" for AudioEngine, AudioDevice and said UserClient Class ).

With XCode 12 the issue is still there and the workaround with 9.4.1 prevents me from building a KEXT on Apple Silicon. Are there any news for a "true" solution?

Now I found the basic reason: I my source code for subclassing IOAudioEngine certain functions are declared as "virtual" but some of these functions did only exist in my subclass, so keyword "virtual" finally was wrong. After fixing this I can build the KEXT with XCode 11 and even XCode 12 and it is loaded in 10.15 and 10.16. XCode 9.4.1. seems to behave different, so the wrong "virtual" it did not lead to problems in loading the KEXT.

I run in same problem now (on my first steps with DriverKit): crash after loading DEXT for unsatisfied entitlement, downloaded provisioning profiles does not contain any "USB" related string. Description of profiles on developer-area says: Enabled Capabilities DriverKit USB Transport - VendorID, In-App Purchase. So my question is: Did you find a final solution?