Since the last update I was faced with the same problem on Ubuntu 20.04 with a broadcom BCM4312.
The described solution with 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
worked well for me!!
Since the last update I was faced with the same problem on Ubuntu 20.04 with a broadcom BCM4312.
The described solution with
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
worked well for me!!