WiFi is not working on a fresh-install Ubuntu 20.04

I'm using Macbook Pro Late 2011 to install Ubuntu 20.04 on it. WiFi was working fine when trying Ubuntu from Live USB, but it wasn't after the installation. I couldn't find the WiFi adapter in Network settings.

First, when I opened Software & Updates > Additional Drivers, I saw:

Broadcom Inc. and subsidaries: BCM4331 802. 11a/b/g/n (AirPort Extreme)

The option Do not use the device  below it was checked and then I check another option to use the device and clicked Apply Changes but failed.

Second, I mounted the Ubuntu installation ISO file as a CD-ROM (using commands in Terminal) then opened Software & Updates again and selected Ubuntu Software tab. Under Installable from CD-ROM/DVD label, I checked Cdrom with Ubuntu 20.04 then repeat the first step but still no luck.

The solution below (that I copied from here) worked. 

1. Extract the Ubuntu installation ISO file (ubuntu-20.04.*.iso) to ~/Downloads folder then open Terminal and run:

> sudo chmod -R 777 ~/Downloads/ubuntu-20.04.*

2. Find the broadcom firmware on another machine:

- Download broadcom-wl-6.30.163.46.tar.bz2 (or later) from here or my backup.

- Extract it to ~/Downloads folder

3. Run the following commands in Terminal:

> cd ubuntu-20.04.*/

> sudo dpkg -i ./pool/main/b/b43-fwcutter/b43-fwcutter_019-4_amd64.deb

> cd ~/Downloads/broadcom-wl-6.30.163.46

> sudo b43-fwcutter -w /lib/firmware broadcom-wl-6.30.163.46.wl_apsta.o

 

> sync

> sudo modprobe -r b43 

> sudo modprobe b43 

4. Check the Network settings again and the WiFI icon should appear.