Yes and No...
Ductless Heat Pumps will heat your home even when the temperature outside drops below 0 degrees.
All of the Ductless manufactures recommend having a secondary heat source (Furnace, Boiler or Electric).
I personally use only a Ductless Heat Pump in my recording studio. I never had a problem keeping that room warm, even when it was -5 degrees outside.
For more information on Ductless Heat Pumps go to: https://www.airinchvac.com/ductless-heating-cooling.html