>>44919
>Maybe the simplest is to cut old wires at the connections, seal them off and leave them in the walls and ceilings, and screw plastic channels outside the walls and ceilings where the new cables can run.

Yes, that is "easy" solution but it is also looks more temporary than permanent. There is one cable that already made that way, for new washing machine.

>A more elegant solution: leave the old cables in like above, and cut new channels into the walls, where new tubes can be put for the new wires. This however a dirty work with dust and debris.

That is how most flats are renovated here. New cables in tubes are placed on ceiling then closed by fake ceiling with plates or such. Or same at floor if there is also floor-leveling work (adding few cm of new floor). Then wires go into cable channels under plaster in walls.