As a backgrounder, I used an Ubuntu 18.04 64bit Desktop ISO sometime Dec 2018. Most of the basic stuff worked except the touchpad. I also read that there might be some issues with Nvidia and the audio output of the HDMI port but wasn't planning to use it just yet. The touchpad however was a big deal especially I don't usually have a mouse at hand. This once again led me to journey the vast forum pages in the internet to find and eventually compiled the answer in this post.
You may have landed to some answers where you need to install "i2c-tools" package as it was hinted in the BIOS settings for touchpad that you needed i2c drivers, but since you landed here means that didn't work. Changing the BIOS setting from "Advanced" to "Basic" wasn't an option for your either because of the touchpad functions when you go back to Windows.
The next thing I did was to install the Nvidia proprietary driver package, since touchpad input is usually associated with the graphics card... which also did nothing.
Another one would be to install the "xserver-xorg-input-synaptics" package as the default libinput package wasn't enough for our machine... and once again it didn't do anything.
I was about to give up but saw a suggestion in another forum page to sort-of force synaptics to be used for detection of touchpad input. It required you to modify the synaptics xorg config file and made sure to have the following:
Identifier "touchpad catchall"
Option "TapButton1" "1"
Option "VertEdgeScroll" "1"
Now most of the stuff was already (uncommented) in the config file except the last 2 "Option" lines. I just added those, restarted, and then my touchpad finally worked!
To summarize all what happened or what I did, here's a recap along with some of the commands used (to help those linux beginners):
1) Install "i2c-tools"
sudo apt-get install i2c-tools
2) [I think this can be optional] Install the Nvidia Proprietary Graphics drivers. You can do this graphically by going to the "Software & Updates" -> Additional Drivers -> enable the Nvidia proprietary drivers.
3) Install the xserver synaptics package and do a restart
sudo apt-get install xserver-xorg-input-synaptics
4) Modify the config file located at /usr/share/X11/xorg.conf.d/70-synaptics.conf (or the XX-synaptics.conf) and append the necessary stuff I mentioned earlier. You can use your preferred text editor. Do a restart once you have saved the settings.
Here's an output of my "xinput --list" when my touchpad worked. The ELAN touchpad finally showed up after the stuff I did.
⎡ Virtual core pointer id=2 [master pointer (3)]
⎜ ↳ Virtual core XTEST pointer id=4 [slave pointer (2)]
⎜ ↳ ELAN0504:01 04F3:3091 Touchpad id=12 [slave pointer (2)]
⎣ Virtual core keyboard id=3 [master keyboard (2)]
↳ Virtual core XTEST keyboard id=5 [slave keyboard (3)]
↳ Power Button id=6 [slave keyboard (3)]
↳ Video Bus id=7 [slave keyboard (3)]
↳ Video Bus id=8 [slave keyboard (3)]
↳ Power Button id=9 [slave keyboard (3)]
↳ Sleep Button id=10 [slave keyboard (3)]
↳ HD WebCam: HD WebCam id=11 [slave keyboard (3)]
↳ AT Translated Set 2 keyboard id=13 [slave keyboard (3)]
↳ Acer WMI hotkeys id=14 [slave keyboard (3)]
Credits to the participants/contributors in the UNIX stackexchange I read.