RE: Kernel update help.
I tried to install the DisplayLink driver on Ubuntu 14.04, but it said my kernel was too old. So I used the built-in upgrade tool to 15.04, which worked effortlessly.
At this point, the D3100 dock worked, but the mouse pointer flickered at 2-5 Hz. After a few days, I decided to see if Ubuntu 15.10 would be an improvement. It was! No more flicker!
If you are considering the D3100 monitor dock, it works very will with Ubuntu 15.10 and the new DisplayLink driver. Wahoo!
P.S. This is with a 2014 Dell XPS 13. YMMV.