Self-confessed computer nerd jumping in
Depending on the model of Sony Xperia being used, there are some known problems accessing the phone as anything more than an SD card (i.e. storage). Seems Sony decided that Mac & Windows users are all they can be bothered actually supporting (though, as I said, there is some success in getting access to the SD card).
Whilst both Android & Ubuntu are simply* versions of Linux, their connection is via the USB drivers & protocols. Windows & Mac install alot of drivers automatically and, what they don't, can be easily downloaded from the Internet as soon as you plug the device in. Linux tends to be a bit more of a pain about these things and I'm a nerd that likes it.
* Of course, the differences between Linux distributions are far from simple!