Nest and Ecobee can work with many common 24V heating and cooling systems, including some heat pumps

https://westusa2.blob.core.windows.net/hvac-plumbing/when-your-mini-split-ices-over-in-winter.html

Nest and Ecobee can work with many common 24V heating and cooling systems, including some heat pumps, though certain homes may need a C-wire or add-on power accessory.