Ubuntu – Lenovo Z50-70 realtek dirver RTL7823BE wi-fi does not connect

Please do:

sudo apt-get purge --remove bcmwl-kernel-source
sudo modprobe -rv wl
sudo modprobe -v brcmsmac

if there are any errors complete the rest of the commands anyway.

We may have to unblacklist some modules if the purge command does not do it for us.

The command in the post you linked is:

echo "options iwlwifi bt_coex_active=Y swcrypto=1 11n_disable=1" | sudo tee /etc/modprobe.d/iwlwifi.conf

It will over-write the existing text in the file /etc/modprobe.d/iwlwifi.conf. It should have read:

echo "options iwlwifi bt_coex_active=Y swcrypto=1 11n_disable=1" | sudo tee -a /etc/modprobe.d/iwlwifi.conf

The '-a' modifier appends the new text to the end of the existing file.

In Ubuntu 15.04, the default file reads:

# /etc/modprobe.d/iwlwifi.conf
# iwlwifi will dyamically load either iwldvm or iwlmvm depending on the
# microcode file installed on the system.  When removing iwlwifi, first
# remove the iwl?vm module and then iwlwifi.
remove iwlwifi \
(/sbin/lsmod | grep -o -e ^iwlmvm -e ^iwldvm -e ^iwlwifi | xargs /sbin/rmmod) \
&& /sbin/modprobe -r mac80211

That text is necessary to properly unload and reload the module iwlwifi if necessary. I suggest you do:

gksudo gedit /etc/modprobe.d/iwlwifi.conf

Use nano or kate or leafpad if you don't have the text editor gedit. Copy and paste the text I included above the line you added. When you are done, it should read like this:

# /etc/modprobe.d/iwlwifi.conf
# iwlwifi will dyamically load either iwldvm or iwlmvm depending on the
# microcode file installed on the system.  When removing iwlwifi, first
# remove the iwl?vm module and then iwlwifi.
remove iwlwifi \
(/sbin/lsmod | grep -o -e ^iwlmvm -e ^iwldvm -e ^iwlwifi | xargs /sbin/rmmod) \
&& /sbin/modprobe -r mac80211

options iwlwifi bt_coex_active=Y swcrypto=1 11n_disable=1

Proofread carefully, save and close the text editor. You should be all set.