I’m running Kali on an OLD Macbook Air. I ran an update today and was having trouble completing the initramfs update so I removed the old kernels and rebooted.

Of course when the system came back up, the wifi adapter wasn’t working. Missing firmware. The Macbook is using a Broadcom 43224 device.

After some troubleshooting and internet researching, I found I needed to install a brcmsmac package. Thanks to this debian wiki page. I grabbed an Alfa USB wireless adapter to get online in the meantime.

These are the commands I ran. Simple fix, just using apt-get and modprobe. 

sudo apt-get install firmware-brcm80211
modprobe -r brcmsmac
modprobe brcmsmac

The wifi adapter came back up after that. Just leaving this here in case it can help someone else too.