Hi,
Have you attached the support logs somewhere? I cannot see them linked in your post
PS: For Mac problem, see support.displaylink.com and navigate to the section for Mac. In short, what you see (clone mode, with one extending screen driver through Airplay) is current behaviour on post-10.13.3 macOS versions - with an exception of 10.14 Mojave, where extended desktop support is restored.
Thanks
Michal