I am running High Sierra on a Late 2017 27" iMac. I proceeded to install Mojave, and it installed, but none and I mean none of my networks cards were available. No Ethernet no WiFi, I tried to install them via System Preferences Networking. The cards were not available to the OS. I reinstalled High Sierra, and tried again same problem. I would have reported this to Apple, but the Feedback assistant doesn't work when there isn't a network card. Any ideas?