Yup. When I bought the house, the sellers said that they suspect that the main chimney is fractured. So I checked those modern stainless systems to install inside the flue. But before doing that I asked the professional chimney-sweepers to inspect the chimney, and they said that the main flue is safe to use.

At the moment it seems that I still have that main flue intact. There is another flue from the main room, an opening for air ventilation, and then the parallel chimney from the smaller room - all of these three were connected to the second flue. And it it that connection which got fractured. So, maybe for the coming winter I'll just temporarily abandon the second flue altogether, using only the first flue for the kitchen stove.

That brings me to a question: Watching the videos from inside your house, it seems that your house has some sort of channels for circulating warm air to different rooms? Is it so, and if yes, how does it work? Is it designed to have a blower to circulate the air?