Is there any indoor heating method without coal and electricity in winter?

Anything that can produce energy conversion will do.

The essence of taking heat is that the energy of matter is converted into heat energy.

Because there are fewer substances that can release energy in normal contact, only coal and electricity are misunderstood. This is only relatively easy to obtain, and specific nuclear energy is also possible. It is not impossible to develop now. If nuclear energy can be controlled well, it is impossible to say that it will be a small nuclear reactor in the future.

I've also heard of something called antimatter. I heard that it is available now, but it is difficult to get it.

When it comes out, it is equivalent to the fuel tank of a car and can be reduced to the size of a lunch box. The mileage is that the car is scrapped and he can't use it clearly.