Note for users with older mini PCIe wifi cards such as the 2006 MacBook BCM94321MC: there is no native support in macOS Sierra for your devices. AppleAirPortBrcm43224.kext has been omitted from IO80211Family.kext Plugins in macOS Sierra.
Below is a list of all devices that have been excluded from macOS Sierra:
Broadcom Device IDs
pci106b,4e
pci14e4,4311
pci14e4,4312
pci14e4,4313
pci14e4,4318
pci14e4,4319
pci14e4,431a
pci14e4,4320...
Some Broadcom Mini-PCIe WIFI Devices Unsupported in macOS Sierra
Below is a list of all devices that have been excluded from macOS Sierra:
Broadcom Device IDs
pci106b,4e
pci14e4,4311
pci14e4,4312
pci14e4,4313
pci14e4,4318
pci14e4,4319
pci14e4,431a
pci14e4,4320...
Some Broadcom Mini-PCIe WIFI Devices Unsupported in macOS Sierra