Step-by-step – Debian Stretch Install Broadcom Wifi Driver Offline Easy Guide

Installing

3. 3. Downloading

   Download broadcom-sta-dkms for Debian GNU/Linux

   broadcom-sta-dkms Package

   Downloading broadcom-sta-dkms for Debian

   Provides to Grab both broadcom-sta-dkms and dkms.
   Store them in a Separate Folder.

4. 4. Installing

   Then to Install broadcom-sta-dkms Driver
   Now Change to the Target with:

   cd ~/Downloads/[MYDIR]

   (But if you are in Trouble to Find the Location on Terminal then See: How to Access Downloads Folder from Browser.)
   And then simply play:

   sudo dpkg -i *.deb

5. 5. Loading

   Finally, to Load Broadcom Wifi Driver
   Execute:

   sudo modprobe -r b44 b43 b43legacy ssb brcmsmac bcma

   sudo modprobe wl