Broadcom Wireless Drivers [14e4:4331] (rev 02) Macbook Pro Ubuntu 18.04

I have installed Ubuntu 18.04 on my old Macbook Pro, Everything is working great except for the wireless driver.

lspci -nn -d 14e4: gets the following:

02:00.0 Network controller [0280]: Broadcom Inc. and subsidiaries BCM4331 802.11a/b/g/n [14e4:4331] (rev 02)

lspci -vvnn | grep -A 9 Network gets:

02:00.0 Network controller [0280]: Broadcom Inc. and subsidiaries BCM4331 802.11a/b/g/n [14e4:4331] (rev 02)
    Subsystem: Apple Inc. AirPort Extreme [106b:00f5]
    Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
    Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
    Latency: 0, Cache Line Size: 256 bytes
    Interrupt: pin A routed to IRQ 0
    Region 0: Memory at a0600000 (64-bit, non-prefetchable) [size=16K]
    Capabilities: <access denied>
    Kernel modules: bcma

rfkill list all gets:

0: hci0: Bluetooth
    Soft blocked: no
    Hard blocked: no

grep b43 /etc/modprobe.d/* gets:

/etc/modprobe.d/blacklist-bcm43.conf:blacklist b43
/etc/modprobe.d/blacklist-bcm43.conf:blacklist b43legacy
/etc/modprobe.d/blacklist.conf:# replaced by b43 and ssb.

and sudo dmesg | grep b43 does not get anything in return.

I found this great post on how to install Broadcom Wireless Drivers, and have tried the firmware-b43-installer package and the linux-firmware option, but it does not work in my case, as after installing the package and reboot, the system still cannot detect a wifi adapter.

As the great post mentioned that if my Broadcom card has a different pci.id that cannot be found in the list, I can ask a new question. So here I am.

Many thank.

/etc/modprobe.d/blacklist-bcm43.conf:blacklist b43

It appears that you attempted to install another driver which blacklists the driver b43 which is needed for your device. Let's correct it:

sudo rm /etc/modprobe.d/blacklist-bcm43.conf
sudo modprobe b43

Your wireless should now be working.