Hm, I ordered the adapter to look whether it would initiate thunderbolt alt mode, but I just found it working as a usb-c adapter cable to connect to an external display.
I changed the page to reflect my findings and added the information about my firmware. Maybe @Hristo needs to update to get it working, too.
The adapter is really nice since it seems perfect for presentations while travelling. Also it is quiet cheap when bought directly at the page of CABLEDECONN (at the time of writing 15US$ + shipping).
I also added a reference to the page to the information how to find the firmware versions used in the L5 that do influence docked mode.