https://www.dell.com/en-us/work/shop/overview/cp/linuxsystem...
This link shows their Linux lineup. Seems they cover all 3 laptop sizes 13/15/17 both in an ultra book form factor and a bulkier port rich model. What more were you hoping for? I personally think it's a good thing they limit the pre-installed Linux models to their professional/business line of laptops. Supporting Linux on every model is probably a waste of time.