I've been doing a lot of research but I can't seem to find an answer to this question.
A plethora of laptops exist that do work well with Linux (I'm using Ubuntu 16.04, but if an answer is available for other Linuxes, it's fine); that I know. Some even include a builtin 4k monitor that works fine.
What seems very hard to get reliable information about is:
Which current (November 2016) portable laptop (max 14 inches, max 2.5kg/5.5lbs weight) can support an external 4k (3840x2160) displayport 1.2 monitor @60Hz, either directly or via an adapter/dock which is confirmed to work reliably?
There seem to be an issue with modern laptops with USB-C-to-DP adapters or docks that aren't properly recognized by Ubuntu, and I'd like an hassle-free solution - in many forums about Dell XPS/Latitude/Inspiron I've seen people saying that sometimes they were able to work it out with custom kernels or arcane configurations, but I use my laptop for work and I don't want to waste too much time at configuring my laptop.
PLEASE NOTE: I expect exact make and models that can be actually bought today in Europe. Don't suggest me the specs, I already know what I'd like, but it seems that the requirements are conflicting enough that I cannot find a brand new laptop that has all of them at the same time.