Right after installing dual boot windows+ubuntu on Lenovo Y520, I found wifi was disabled & was not listing any available wifi.
Did some research and figured out that wifi is being blocked, if you are having same problem give the following steps a try. It worked out for me though.
From the terminal:
sudo modprobe -r ideapad-laptop sudo rfkill unblock all
If this enables wireless, we can blacklist the module in order to make it permanent.
Since we now know that this methods enabled your wireless, let’s make it permanent:
sudo -i echo "blacklist ideapad-laptop" >> /etc/modprobe.d/blacklist.conf exit
Hope it will be helpful, leave comments if you have other solution.