Comment 21 for bug 1878045

@angels After the latest update I had that issue too. Wifi bar in the settings was completely gone. When I typed: "apt purge bcmwl-kernel-source" command I got this message:
E: Could not open lock file /var/lib/dpkg/lock-frontend - open (13: Permission denied)
E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), are you root?

I tried again with sudo prefix and it worked, so if you are still having the issue try this:
sudo apt purge bcmwl-kernel-source
sudo apt-get install broadcom-sta-source
sudo apt-get install broadcom-sta-dkms
sudo apt-get install broadcom-sta-common

Hope it will work for you as well!