Installed Lubuntu 16.04 version no audio now

Before anything, make sure your sound is not muted.

ALSA and PulseAudio don't get together well. They are conflicting each other most of the times. Unless ALSA is specifically required by an app or hardware I recommend using only Pulse (it's newer and better).
First, remove alsa completely by opening a Terminal window and typing:

sudo apt-get remove --purge alsa  

Secondly install Pulse:

sudo apt-get install pavucontrol

pavucontrol is the graphical interface for Pulse, but it will install Pulse completely (as its dependencies).

And finally, type:

gksu pavucontrol  

A Pulse window should come up with many tabs and options. Make sure the inputs and outputs matches your connection (hdmi, usb, headphones, etc), and make sure Pulse is using the correct audio card (on-board, dedicated, external usb/hdmi device, etc). E.g. When connecting laptop to large screens via hdmi, Pulse might detect the hdmi audio card as external output device with specific brand (not necessary the same as vendor brand). If so, you must choose that external card as output to make audio work.

Be aware that Ubuntu doesn't support hdmi hot-plugging! After disconnecting hdmi device, Pulse (or ALSA) will not fall-back to previous settings. You have to change the settings (again) and then restart the Pulse audio service by log out + log in in order to make things work again.

I tried everything that was ever recommended online, I was only able to fix my PC sound issue by running the following commands:

killall pulseaudio
rm -r ~/.config/pulse/*
rm -r ~/.pulse*

Some directories may not exist, that is OK.

then:

pulseaudio -k

then reboot

I found this solution here, there are also some other recommended solutions if this doesn't work.

I did all the above to no avail.

What did work was simply unplugging my desktop speakers from headphone jack and plugging them into the Line Out jack.