Hello FMK,
the problem is the ARM hardware architecture from RaspberryPi.
Here is an official statement from the kernel developers of RaspberryPi:
The config option for the DRM module is DRM_UDL,, the equivalent legacy frame-buffer one is FB_UDL, both have no dependencies that aren't already met in the standard kernel build on the Pi. Note that these only work with the older USB 2.0 DisplayLink devices, the USB 3.0 ones use proprietary encryption on the USB link to satisfy HDCP requirements, and thus don't work with Linux (and are not likely to ever work with Linux).
I have the same problem with an
USB 3.0 monitor.
According to rumors, an ARM PC with USB 3.0 (e.g. Odroid) should be able to run a USB 3.0 monitor.
Best regards
Michael