the sample YAML was missing the hst-hosts node between the /hst-platform root node and the virtual host group node. I have updated the documentation to show this node now. That will probably solve your problem.
thanks a lot four your quick reply and fixing the docs!
Actually I already configured a host node yesterday, as well as the virtualhostgroup/virtualhosts below the hst-hosts node. However, with a fresh look today I spotted a misconfiguration on my behalf, i.e. a missing virtualhost node and wrong node typing.
Now the virtualhosts config is working and externally accessable - great!