A comment
I use the boiler from Zota, model Smoke. Work more satisfied than not. It has small dimensions, it is convenient to heat 40 cm with firewood. In addition to firewood, you can use coal or install tena, for the latter there is a special opening on the boiler. Using it is simple and convenient, the coolant heats up quickly, and thanks to this, the room heats up in a short period of time.
Tena are controlled by automation, able to maintain the desired temperature, both in a heated room and in a coolant. In fact, it is practical and convenient, for example, at night, there is no need to specifically get up and flood the boiler.
I also really like that the hob is installed on the boiler, the wife constantly cooks on it when we drown.
I don’t like a few things in the boiler: the coolant cools quickly, so without heating elements it will be bad, firewood burns out quickly.
pros
Quick heating of the room, compactness