I’ve had a multi sensor in my fridge working just fine for 6+ months that hovers around 40. Not sure how I feel about using it for a freezer though others have said it works.
Personally for a freezer I’d get something like a Adafruit DS18B20 temperature sensor + a ESP8266 running ST_Anything. The sensor is rated for -67* F to +257* F and is waterproof so if you already have a way to route it into the freezer I’d think it’s the best way to go.
I don’t know of a actual Zigbee or Z-Wave sensor that’s made for freezers simply because of battery life being sketchy.