If it is not possible to drill floors or internal walls so maybe you can consider to pass fibers along gutters down to the basement to make the connection point there? It should be safe and easy if you put them in separate thin pipes mounted to gutters.
Idea out of the box but no so fresh as once I even considered mounting on a wall special dummy external chimney pipe just for wires . It was a historical building and solution >>external chimney + one hole in a wall per level" was more acceptable by a conservator than drilling through wooden floors and ceilings on each level with an old “do not ask what it consist of” historical insulation between them.
EDIT:
Stupid me … so simple idea if only you can use it: internal ventilation ducts.