Ars Technica takes a look at Ubuntu Touch
Today there are four devices onto which you can easily load Ubuntu Touch: the Galaxy Nexus, the Nexus 4, the Nexus 7, and the Nexus 10. As Android reference devices, these phones and tablets are all pretty easy to unlock and manipulate, and their software and drivers are all readily available from Google and the Android Open Source Project (AOSP). Because Ubuntu Touch relies on a few low-level parts of Android to work—the Linux kernel, graphics and audio drivers, and software for using the phone's cellular radio—porting the OS to any other device requires that software to be available.Exploring Ubuntu Touch, the other Linux OS for your phone
A considerable amount of work has been done to port Ubuntu Touch to a smattering of other phones and tablets, the full list of which can be found on this Devices page. Images for these devices aren't hosted by Canonical, but the flashing instructions and status pages are all linked there. At the time of writing, the instructions that we cover here won't apply to any non-Nexus devices.