I have a ThinkPad T560 with Broadcom wifi card:
04:00.0 Network controller [0280]: Broadcom Limited BCM4356 802.11ac Wireless Network Adapter [14e4:43ec] (rev 02)
It is not covered in Installing Broadcom Wireless Drivers. Following this topic by installing firmware-b43-installer
and linux-firmware
does not help.
On Ubuntu 17.10 it gets the proper driver (brcmfmac), sees my wireless networks but refuses to connect to any that are protected with WPA/WPA2 - it just keeps asking for the password.
dmesg show something like this which is a bit weird:
[ 8126.093543] brcmfmac 0000:04:00.0: Direct firmware load for brcm/brcmfmac4356-pcie.txt failed with error -2
[ 8126.530782] brcmfmac: brcmf_c_preinit_dcmds: Firmware version = wl0: Oct 22 2015 06:16:41 version 7.35.180.119 (r594535) FWID 01-1a5c4016
[ 8126.652096] brcmfmac 0000:04:00.0 wlp4s0: renamed from wlan0
I tried to download brcmfmac4356-pcie.txt
file from some linux-firmware related site but that didn't help (although the line disappeared from dmesg)
This problem is super-frustrating as I remember I found a solution when 17.10 was launched but I cannot find it now.
On Ubuntu 18.04 LTS the card doesn't work at all.
I have a similar situation with the brcmfmac driver and achieve a connection by going to the terminal immediately after logging in and entering;
sudo modprobe -r brcmfmac
Then wait a couple of seconds and enter;
sudo modprobe brcmfmac
You might have to forget the connection, re-add it ticking start automatically and then reboot and try the commands again.
Also read about the naming of firmware files for your chipset here