This thing can be fixed by having low temperature floor heating. It does imply that your heat pump should be air to water or water to water versus a mini-split which is air to air.
Low temperature means only a couple of degrees higher than ambient. It just constantly radiates. That also mean that heat pump needs to work less hard.
It does require a significant amount of insulation to ensure you don't lose the heat immediately.
And because of the high mass it means that interruptions aren't noticed.
If it works great at 10c and OK at 0c and just a little bit at -10c but extracts no useful heat at -20c and your local weather has lots of time below 0c, then no amount of low temp floor heating will help.
This is just plain false. The entire country of Finland (and Sweden, and Norway) installs pretty much only air source heat pumps, air-water heat pumps, or ground source heat pumps in all renovations or new built buildings.
In the north of the country you end up heating your house for some days with resistive heating, but it is still cheaper than any alternative source.
Low temperature means only a couple of degrees higher than ambient. It just constantly radiates. That also mean that heat pump needs to work less hard.
It does require a significant amount of insulation to ensure you don't lose the heat immediately.
And because of the high mass it means that interruptions aren't noticed.