The XPS 13’s ram is soldered in, so was never upgradable like the X240/X250’s was.
Dell has the XPS 13 Developer Edition, which is the XPS 13 with Ubuntu installed on it from the factory, and with a tested/supported hardware configuration.
To my surprise, it booted straight into Unity, at full resolution, without any issues.
Poking around, it didn’t even need the boot parameter at all.
The laptop comes with a Samsung PM951 512gb, but I took the liberty of swapping it out for a Samsung SM951 512gb.
The PM is a bit more of the mid-range model, while the SM is the top dog.
I then fired up X and found it errored saying no display devices found. Luckily, beforehand I saw a link on Twitter about needing a boot parameter for the Intel graphics.
I applied the setting, reboot, and had a completely blank display.
Luckily, I had a very helpful assistance while debugging all this.
I decided on a whim to just boot he Ubuntu 15.10 Live CD and see how far it got.
I’ve had to deal with Broadcom chips in Macs long enough to know you don’t use Broadcom if you have other options, so I went ahead an ordered an Intel 7265 off Amazon, same that was in my X240/X250. Once opened up, I booted up Windows only in order to check if there were any BIOS or firmware updates to install. First task was to crack it open and swap out the Broadcom wifi for a far better Intel 7265. It was only off Amazon, and it by far beats the reception and support issues of Broadcom.