I've been troubleshooting this issue for two days now, trying various fixes I've found online to no avail. I'm using a Thinkpad X1 Carbon (6th gen) and dualbooting Win10 and Mint (18.3). Wifi works as intended on Win10 but neither NetworkManager nor WICD can recognize any wifi networks in Mint.
Here is output for lspci -v | grep -A 10 -i "Network Controller":
02:00.0 Network controller: Intel Corporation Wireless 8265 / 8275 (rev 78) Subsystem: Intel Corporation Dual Band Wireless-AC 8265 Flags: fast devsel, IRQ 255 Memory at ee200000 (64-bit, non-prefetchable) [disabled] [size=8K] Capabilities: <access denied>
I downloaded the iwlwifi-8265-ucode-22.361476.0.tgz file from Intel's website: https://www.intel.com/content/www/us/en/support/articles/000005511/network-and-i-o/wireless-networking.html
I followed the instructions on this post: https://forums.linuxmint.com/viewtopic.php?t=247531 and ran
sudo cp iwlwifi-8265-22.ucode /lib/firmware/
sudo apt-get install build-essential linux-headers-$(uname -r)
which gave me the following output:
Reading package lists... Done Building dependency tree Reading state information... Done E: Unable to locate package linux-headers-4.15.0-20-generic E: Couldn't find any package by glob 'linux-headers-4.15.0-20-generic' E: Couldn't find any package by regex 'linux-headers-4.15.0-20-generic'
I downloaded the .deb file from here https://pkgs.org/download/linux-headers-4.15.0-20, ran dpkg -i and got the following output:
(Reading database ... 317506 files and directories currently installed.) Preparing to unpack linux-headers-4.15.0-20-generic_4.15.0-20.21~16.04.1_amd64.deb ... Unpacking linux-headers-4.15.0-20-generic (4.15.0-20.21~16.04.1) over (4.15.0-20.21~16.04.1) ... Setting up linux-headers-4.15.0-20-generic (4.15.0-20.21~16.04.1) ... /etc/kernel/header_postinst.d/dkms: ERROR (dkms apport): kernel package linux-headers-4.15.0-20-generic is not supported Error! Bad return status for module build on kernel: 4.15.0-20-generic (x86_64) Consult /var/lib/dkms/ndiswrapper/1.60/build/make.log for more information.
Not sure where to go from here.
For transparency I posted this on the Mint forums as well with no responses.