[Galaxy S III Original Android Development] Androguide.fr:
Ubuntu on Android is a separate project, which will come both as an Android app which allows you to boot Ubuntu desktop when plugged-in to a screen/mouse/keyboard as well as an Ubuntu Touch package allowing to do the same from Ubuntu Touch itself.

My understanding is that this won't be possible unti Mir/Xmir is implemented as the Xserver replacement on both the Desktop and the Phone/Tablet versions of Ubuntu.

Early builds including Mir for the desktop have already been dropped, but Ubuntu Touch still runs Mir at the moment.

Keep in mind that even if the Ubuntu Edge campain had been fullfilled, the devices wouldn't be shipping until next year so just because they announced it doesn't mean it's ready just yet. And there hasn't been a "real" ubuntu edge produced yet, only precision-engineered mock-ups with the real weight, but no hardware/software running on it.

But yeah, in the end, booting Ubuntu for Android should be available in the mainstream builds so any (powerful enough) device can run it.

AFAIK the convergence feature-set should be released at about the same time as Ubuntu 14.10 and the official release of Ubuntu Touch (i.e: not a beta/preview anymore, ready for prime-time).

EDIT: But in the meantime, you can very easily run Ubuntu Desktop out of your i9300 when plugged to a computer when using both Android and Ubuntu Desktop.

On Android:

First way:

Download DriveDroid from the playstore

Download an ubuntu image from the ubuntu website

put it on your device in /sdcard/Download/images

Select it from the app, plug your device to your pc, reboot it, select the device from your BIOS/boot menu and enjoy!

2nd way:

On Android, download "Complete Linux Installer", free from Google Play

On your pc, download the Ubuntu image you want (i.e: with Unity or xfce) from http://sourceforge.net/projects/linuxonandroid/files/Ubuntu/ (you can also download the image from the app if you want)

In the app, go to "Launch", tap settings --> add, insert a name and select the image you downloaded. Then hit "Start Linux".

This will start the terminal, it will ask you some configuration info the first time, then you're in the ubuntu shell!

[*}At this point, you can use a VNC client app to go into GUI mode from your phone, or you can use VNC client on your pc to have the full desktop experience, running out of your S3.

On Ubuntu Touch:

After having done the above, you can simply grab the scripts from /data/data/com.zpwebsites.linuxonandroid/files and use them in Ubuntu Touch, then same thing, just use a VNC client to connect

It just doesn't work if you just plug it into a standalone screen, you need a computer.

Although, arguably, we could stream the screen from the device while using a VNC app with a MiraCast dongle or even maybe a ChromeCast using koush's AllCast hackery, and then it would work.

I personally use both DriveDroid and the LinuxOnAndroid scripts all the time.

And honestly, with xfce it's pretty smooth when running natively through VNC on the S3 with some overclocking.

With DriveDroid you get very good performance, at least a lot better than with a live usb key, given we have an eMMC and the other resources used are from the pc you're plugged into.