Identifying Your Broadcom BCM43xXx Chipset:

With this information, you may assess what drivers are supported for your card, and how to switch to a different driver from the instructions below.

To identify a card that was installed inside your computer prior to purchase, please open a Terminal and execute:

sudo lspci -vvnn | grep -A 9 Network

This will display:

Network details

Prepare the System

If you have just installed Ubuntu, you will need to build an index of available packages before we can install your driver if you have not done so already:

sudo apt update

I would even go so further as to update the Ubuntu list of PCI.IDs:

sudo update-pciids
Installing the Package

Assuming you used the PCI.ID 14e4:4320 rev 03 as found in your search above, and then looked at the table below and found that the correct package to install is the firmware-b43-installer, we then proceed to simply install this package in the terminal:

sudo apt install firmware-b43-installer

and then reboot

sudo reboot