The hacking section made clear that fencing or rooting a commercial device are fragile solutions that do not meet the requirement of a long term stable design.
When applying open source software on an open hardware platform, the Kodi suite appears to be the most mature project with also a promising set of plugins for Dutch TV service providers available.
With these preliminary findings we stop gathering more information on maker's smart-TV projects and start out experimenting with Kodi.
See also (in Dutch):
https://www.ct.nl/workshops/raspberry-pi-als-mediacenter/