I have an ecobee thermostat that I manage locally iver WiFiusing the HomeKit integration, but I’d stop short of recommending it to new users.

1. Ecobee used to support developer access to their cloud API for controlling the thermostat and collecting efficiency data, but stopped issuing new API access tokens in the last couple.of years. They have no plans currently to reopen access.
2. The thermostat requires 24V from the furnace to run the display and wifi stack. They provide an adapter you can install if you have available free leads at bother ends of the thermostat control cable. I had to splice a new wire into my furnace, since it didn’t have a 24V common terminal on the control block
3. Some advanced thermostat features require the app. I am not sure whether the app uses cloud or local control when on the same WiFi.
4. Not all features are available through the HomeKit integration. I can change the thermostat mode among Auto/Heat/Cool/Off, manage the blower fan mode and manage the heat/cool set points.
5. Data logging. The damned thing does log activity back home, and the data is only available in the app or on thr web portal.

Other than that Mrs Lincoln, how was the show? I haven’t been unhappy with the ecobee. I shied away from Honeywell because the last Honeywell unit I had before the thermostat I was replacing tended to cycle my furnace too fast during cold snaps, and it would put the system into thermal protect mode. There was no way to widen the hysteresis except by manually setting the temp high, run Tue house up to that temp, and then lower the setpoint and let the house take longer to cool.