Thanks for the pointer, but that unfortnately does not work, that is the same extension I used before.
It does not error out, but just plainly does not work for K2.
The author says it here:
www.heise.de/newsticker/foren/S-Re-VR-und-3D-Drucken/forum-241727/msg-22696618/read/
For K2 you need to buy the subscription version, and that is 20 euros / 30 dollars, which is pretty steep for a litte extension for my non-commercial site that does not earn me any money at all.
So for correction, the extension in the K2 directory should be switched from free to commercial.