I don't know about Landyacht 92, but we got our antenna wire pulled - went through the floor channel as you said from passenger side to drivers side, then went through the back of the lower cabinets, behind the sofa and up the wall beside the door frame (for now). We will put a piece of channel there to cover the wire.
Unfortunately in the process of hooking up to the antenna booster we found that the switch in the booster was shot……
Sort of like the operation was a success but the patient died
However that too shall be fixed!
Thank you, Trident, for your description of how this is done.