I got the following info from a post KerfufflyKitty posted in the old forums back in January 2018. I think the info is very useful for those with Broadcom WiFi cards/chips, so I'm going to add the info to the new forums.

You'll need to temporarily use an ethernet cable.

(01) If you have just installed Solus, perform a system update either via the Software Center or drop to the command line and enter:

sudo eopkg up

If you use eopkg, answer yes if there are additional packages to be installed.

(02) Using Software Center, go to Applications - Hardware and install the applicable/appropriate Broadcom driver:

broadcom-sta-current is for the current Linux kernel
broadcom-sta is for the LTS Linux kernel

To determine what kernel you have, enter the following from the command line:

inxi -S

If the value for Kernel is higher than 4.9.x (as of Solus v3.9999), you have a current kernel.

To install using eopkg:

eopkg it broadcom-sta-current
--or--
eopkg it broadcom-sta

(03) From the command line, enter the following:

echo "install wl /sbin/modprobe cfg80211; /sbin/insmod /lib/modules/\$(/bin/uname -r)/kernel/drivers/net/wireless/wl.ko" | sudo tee /etc/modprobe.d/hackboot.conf
echo "wl" | sudo tee /etc/modules-load.d/wl.conf

(04) Restart the computer.

(05) Use the appropriate credentials to connect to your router using the NetworkManager Applet.

    if you are switching kernel from current to lts and couldn't get it work,
    then from the command line enter following :
    sudo depmod -a
    and thats it !!

    No, Broadcom cards/chips don't work after intially installing Solus. Thanks for that tip though.

      downhill That's not remotely accurate. Most broadcom cards work fine after installing the broadcom-sta-current package and there are quite a few that work without even needing that. You will need to restart your computer for the Kernel to detect the hardware and load the new modules. I am unsure why your specific card requires that additional step, but if it is anything like what I have seen, it probably isn't officially supported by the driver.

          DataDrake My response was accurate. After initially installing Solus, a Broadcom WiFi card/chip is not operable UNTIL you install the driver and reboot.

              I have a broadcomm Wireless Cars and it works without fiddling

              Mine did not. There were a few posts about the issue in the old forums. Unfortunately, that's all gone now.

              23 days later
              21 days later

              The Broadcom drivers available with Solus do not work for all models (specifically for those below bcm4312). I have an old Dell laptop with the bcm4311, and it was always a hassle to get it installed in any version of Linux (Manjaro being the exception, as the correct drivers are included with the ISO) until I read somewhere that once the Broadcom drivers were properly extracted, they could be copied and used on any system. So, if anyone is struggling with installing Broadcom wireless drivers for a bcm4311 (it may work for other models also), I have uploaded the b43 firmware folder and if you follow the instructions below, it should install without a hitch.

              Download the archived file b43.tar.gz to your Downloads directory.

              Open a terminal session. Enter or copy/paste the commands in bold.

              you@yourpc ~ $ sudo su
              Password:

              root@yourpc # cd /home/you/Downloads

              root@yourpc /home/you/Downloads # tar -xzvf b43.tar.gz -C /lib64/firmware
              [This will copy the B43 firmware folder and its contents directly to your /lib64/firmware folder and list each file as it copies.]

              root@yourpc # exit

              Close your terminal session and all other open applications.

              Reboot your system.

              Your Broadcom wireless should start automatically at boot.

              10 days later

              downhill - - - dang I have been messing with this silly Broadcom in this old Gateway Laptop and nothing was getting it to show the WiFi wireless network in house or neighbors.
              All I did was copy and paste what you had Downhill and did the restart and it works like a freaky champ on restart, shows mine and the 6 others I can tag in to.

              I owe you a beer at the pub buddy.

                  fishyman65712 I'm glad the information was useful for you. I can only take credit for re-posting the information...KerfluffyKitty deserves the accolades for the how-to.

                      Dang! I gave up hope with my older Dell Latitude with the broadcom drivers in it. I spent days trying to troubleshoot it on ubuntu. When I installed Solus, there was no change. Which I just figured it was a Linux thing in general.

                      I am going to check this out when I get home tonight!

                      Guess I just got lucky with the Dell I picked up, Intel wireless.

                      4 months later

                      downhill Thanks for the help! Spent about an hour of time troubleshooting this and came across this post. Worked like a charm! It may have been a repost but I am glad that you did.

                      Also, big thanks to KerfufflyKitty if they ever get to see this.

                          Cryo You're welcome. I'm glad the information was helpful to you. Thank you for the reply.

                            19 days later

                            downhill after installing the driver i couldn't get it to work.. these other steps got it to work thank you..

                                5 days later

                                loudtrees You're very welcome. I'm glad the tip helped you out. Thank you for the expression of gratitude.

                                  5 days later

                                  Hello,

                                  I have updated my laptop yesterday. Unfortunately, since the update, my Broadcom BCM43142 doesn't work anymore.
                                  A few months ago, I get my wifi working thanks to the instructions of this thread.
                                  I tried to reinstall the driver, following these instructions with no success.
                                  Maybe I will wait for some updates.

                                  5 months later

                                  Although this thread is old, I though I'd document this here in case it helps someone searching on Broadcom Wireless issues.

                                  The Hardware Drivers app found a Broadcom device and I installed the drivers, but the wireless still didn't work.

                                  Wireless card
                                  Device 14e4:4359
                                  BCM43228 802.11a/b/g/n

                                  I've found the solution above, from @avmasala, worked well here on an old HP ProBook here.

                                  5 months later

                                  Just wanted to point out that as of end of July 2020, after fresh install of Solus 4.1 Plasma on to an older ASUS laptop with BCM43142, still had to follow the steps from post #1 to make WLAN working.