If you’ve ever put your finger on an ESP8266 module when it’s really working, you’ll know what went wrong here: the ESP8266 heated up the board and gave a high reading on the temperature sensor.

Which is how this ESP8266 sensor gadget from ... Currently [Josef] has an SHT21 humidity/temperature sensor and a BH1750 light sensor slotted into the headers on the top side of the device, ...

Adding the arre Temperature Sensor to HomeKit is super easy. Open the Home app, scan the Matter QR code on the device or in the manual, and follow the prompts to assign the sensor to a room.