Can you elaborate on how ChildDext is defined? Also, how to set up the child dext to send and receive data from the parent dext? In our KEXT we had a virtual interface (the parent) and each USB Device instance passes data to and from the virtual interface. Thanks!

I ended up having to compile each OS version with the matching XCode. Build three times, once each for Catalina, BigSur and Monterey. Each with a different version of XCode (11, 12 and 13) using EXPORT DEVELOPER_DIR=/pathto/XCode-NN etc before the xcodebuild