Nothing special is needed for MST except for doing it automatically. Unlike on windows nvidia has always supported horizontal spanning on linux (well ok, for the last 10 years I have been using their video cards they have).
Its over display port instead of DVI but I basically have been using MST (horizontal) spanning on my 4k displays on linux since 2005.
Here is a picture of my older model 4k monitor getting 60hz @ 3840x2400 (higher than 3840x2160), which required genlocked inputs via two dual link DVI driven off a dated geforce GT 8800 (image is from 2010):
The linux drivers may not do it out of the box for you but it should be extremely easy to set it up yourself as long as each input is detected and can be used like any other DFP device. For quite a while now nvidia drivers have supported MST (more for display hubs I believe) so it should work just fine if you know what your doing.