I meant in heat pumps in cars due to size constrains. For homes there are heat pumps that work even at minus -30C, but one just cannot fit that into a car.

And I really do not get why there is no even option to have a diesel heaters in cold climates. It adds like 100 kilometres per long trip for a litre of fuel when it is cold and allows to use smaller and cheaper battery in EV.

you're not making the point you think you are. The average January temperature in most of Norway is about 10 C higher than in most of Yukon and Alaska. Norway just isn't that cold.

That said, heat pumps absolutely do work in -20 C. I would know because i have two at home and one in the car. All three worked just fine at -25 C this past winter.

How many homes have heat pump as their sole heating?

That's a useless statistic without knowing if it's their sole heat source. Just based on costs, I'm betting there's a lot of wood stoves and pellet stoves kicking around.