Ubuntu 16.04 - only connecting to ethernet, no wifi option

The issue

I recently installed Ubuntu 16.04 on a windows machine. Everything seems to be working fine, except for the fact that wifi doesn't seem to be an option for connections

I still have access to other machines that I can use to transfer packages offline

What I've tried, that didn't work

googling away, I've found a post from someone saying that I need to use these commands:

rfkill list
rfkill unblock wlan0

and other commands, but then an error appeared saying Bogus unblock argument 'wlan0', which made sense because it wasn't listed in rfkill list

I then tried this, but the final progress bar didn't seem to proceed, as some users complained in the comments

So I then tried installing bcmwl-kernel-source manually, along with the other packages it needed. I did that and rebooted the machine several times, but I still don't see the wifi as an option

The last thing I tried was setting up a new connection using the "edit connections" button from the image above, and set it to what I could see from my other ubuntu machine over wifi, but I still don't see the option to connect through that anywhere.

outputs of requested commands

Output of lspci -nnk | grep 0280:

01:00 Network controller [0280]: Broadcom Corporation BCM43142 802.11b/g/n [14e4:4365] (rev 01)

Output of sudo modprobe ul:

modprobe: ERROR: could not insert 'wl': Required key not available

--

Any help is greatly appreciated