broadcom-sta-source binary package in Ubuntu Focal amd64

 Broadcom STA is a binary-only device driver to support the following IEEE
 802.11a/b/g/n wireless network cards: BCM4311-, BCM4312-, BCM4313-,
 BCM4321-, BCM4322-, BCM43142-, BCM43224-, BCM43225-, BCM43227-, BCM43228-,
 BCM4331-, BCM4360-, and BCM4352-based hardware.
 .
 This package provides the source code for the wl kernel modules. It makes use
 of kernel-package or module-assistant build systems. The alternative
 broadcom-sta-dkms package can be installed instead and might be easier to use
 with simple system configurations.
 .
 The wireless-tools package is also required in order to make use of these
 modules. Kernel source or headers are required to compile these modules.

Source package