I have the same problem as described since I upgraded from KUbuntu 17.04 / driver 1.3.54 (everything was working perfectly) to KUbuntu 17.10 / driver 1.4
I have 3 screens : the notebook's internal, two external connected with a Plugable USB-C triple display (
this one)
Only on third screen mouse is laggy, activity on this screen raises the DisplayLinkManager process (up to 50%). First external monitor does not use DisplayLink but AltMode.