In our new home we don't have an OpenTherm compatible boiler. This is no big problem, but I do need a different device to read the information from the boiler. Our Nefit boiler uses a different protocol, called EMS.
The boiler we have, has a special "status" port where you can read the information from the boiler. BBQKees created a small device that can do this. This device has support for Home Assistant through MQTT.
When the device is connected, you can adjust the temperature from Home Assistant using the Thermostat widget on the dashboard. This is really easy to setup and use.