No, you are shoehorned into buying a very specific model. It should be no problem whatsoever to choose any model on that site, and select "Ubuntu" for the OS, but you can't. If you go and look (and here I mean actually go and look[0]), the vast majority of machines that you can buy do not have the option to not pay for a Windows license. The choice you get is "Windows 8.1 or Windows 10".

[0] http://www.dell.com/us/p/laptops/xps-laptops