The Dell Latitude E7250 works pretty well, Debian Jessie is missing some drivers and things (eg for Wifi) but Linux Mint (ugh, I know...) works wonderfully well. I haven't tried Ubuntu but I would expect the same experience or better. I was worried about the trackpad being horrible, but I'm actually quite impressed. It's not an Apple trackpad but it's actually pretty decent. (The Disable-Trackpad-While-typing option is almost a requirement though)

Edit: I would emphasize though, if you're going to purchase with Dell, do it as a business (Just pretend you are a business, dont buy it through work). Dell consumer customer support is f#$&ing atrocious. I'm still fighting with them to rectify a problem from an order back in Nov 2015 that I never received. I can't overstate this enough, Dell consumer support is f$#&ing HORRIBLE.