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

https://westus1.blob.core.windows.net/home-blogger/why-your-mini-split-stops-cooling-in-july.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.