How do I know if my Lyric Round™ Wi-Fi Thermostat has HomeKit?
You can tell whether or not your Lyric is a second Generation Lyric Thermostat and HomeKit is enabled by looking for the "Works with Apple HomeKit" logo on the packaging.
You can also tell by the model number located on the back of your Lyric thermostat. These Lyric models are HomeKit enabled: TH8732WFH5002, TH8732WFH5010, RCH9310WF5003, RCH9310WF5011.
To use your second generation Lyric thermostat with HomeKit functionality such as Siri™ you will need a C wire powering your thermostat. Read more about C wires and thermostat wiring here.