On Windows 10, I was able to have two 4K monitors (Dell p2415q) daisy chained on one mini display port, and still use the built in monitor on my laptop.
On Ubuntu 18, I can not use the laptop display. When it will not even detect that I have two screens until I turn off the laptop display - then it works. This took a long while to discover.
Has anyone ever managed to use two monitors daisy chained and the laptop display? I have searched everywhere and no one mentions this. I am using core drivers, nothing special. Would the Xserv drivers help?