I have Linux Mint KDE 18.4 (based on Ubuntu 16.04).
The following problem occurs with both DisplayLink driver 5.2.14 and 5.3.1.

With the default configuration, all works "fine" (more or less, see later).
Once I add a configuration file in /usr/share/X11/xorg.conf.d, the monitor connected to my DL-3900 docking station is no longer detected.

The contents of the file I add is the following:

Section "Device"
   Identifier  "Intel Graphics"
   Driver      "intel"
   Option      "TearFree"    "true"
EndSection

The reason I'm adding this file is to enable the TearFree option. I was suspecting that was the actual problem, but if I replace that file contents with this:

Section "Device"
   Identifier  "Intel Graphics"
   Driver      "intel"
   Option      "TearFree"    "false"
EndSection

hence disabling the TearFree option (as it is by default, when there's no configuration file at all), still the monitor attached to the docking station is not recognized (missing in the Monitor settings in System Settings, where I see just my laptop internal monitor).
Once I move away that file and restart the X session, all is "fine" again.
Any help/explanation would be really appreciated.

When I say that it works "fine" with no configuration file, I mean it works as expected, however I had a problem with 5.2.14 driver (still have to see how 5.3.1 behaves in this regard): right after boot, all works fine. With hours passing by, the whole system becomes slower and slower. After a day of work, it becomes almost unusable. Looking at top or similar task manager, I see the DisplayLinkManager process consuming around 2-3% CPU time constantly upon boot, arriving at a constant ~10% at the end of the day. Apart from this, the CPU seems not to be so much under load, the CPU fan is relatively quiet, it seems like the CPU scheduler isn't pushing the CPU at its higher frequencies any more. I can't explain this behaviour, but the fact that the system become slower and slower over time makes me suspect there's some kind of resource leak in DisplayLink driver and/or manager. Probably some kind of I/O wait issue?
The only fix for this I found is a complete system reboot: just restarting X or the DisplayLinkManager or driver services is not enough.
This problem of course does not happen when I connect the secondary monitor to my laptop HDMI port instead of to the docking station one (otherwise I wouldn't have bothered you).
I know this may be the subject for a completely different report, just wanted to know if it is a known issue and/or if there's any hope it's fixed with 5.3.1 driver version.