No joy!
 

So there was no response to my post for several days, nor that someone would have read my logs, today I returned my Displaylink device.
The following concerns came up during fiddeling around with the adapter:

1) Closed source is ok, but then there should be a functional support process working behind the scenes.
Linux is a rather dynamic system regarding kernel updates. So...do I've to fear every week or so that after a necessary update my third display is wired up? This way, I can't rely on this adapter and the whole system.

2) Announcing a bug in the last driver, but not announcing a release date for the bug fix or, at least, a really proof workaround, smells like low manpower regarding Linux support. So, I don't trust in a stable support in the future.

Perhaps....making the kernel module open source would solve many problems.

Bye