Water-carrying fireplace or wood gasifier - experiences?

This can only make sense if you own enough forest yourself that yields the RM annually and you also like to manage it. After all, you usually need an extra heating room ([Hauswirtschaftsraum] is unsuitable), you need storage space so the wood can dry, and you need the time.

And even then, such a system is still very expensive to purchase. Because here you need the gasifier, a lot of buffer volume, mixing group, controls, etc.

Even in maintenance with easily 4 times chimney sweeps, buffer losses, etc., it is not cheap at first.

In a new building, I would refrain from such technology. It is probably much more worthwhile to sell the wood and buy cheap electricity or gas from it.

That it never pays off was clear to me - but that it involves so much hassle... Compared to that, a classic wood stove in the living room is really a cheap option.

Sure, the stove in the living room simply needs a chimney and possibly separate air supply. There's no fancy stuff or technology involved. Turn it on and it gets warm.

Above all, you are not dependent. With the wood gasifier, you need a backup option so you can go on vacation in winter.