USB 3.0 Ethernet dongle (AX18879) not working with 10.11.4
In Terminal.app issue the command:

sudo nvram boot-args="kext-dev-mode=1 rootless=0"

Remove the NetworkInterfaces.plist file to regenerate a new one:

/Library/Preferences/SystemConfiguration/NetworkInterfaces.plist

Remove the device from System Preferences.app > Network
Reboot your Mac
Plug-in USB dongle
Re-add device in the System Preferences.app > Network