I’ve bought a YoLink hub and temp sensors off amazon to monitor freezers. That’s now morphed into temp sensors, water sensors, motion sensors, controllable plugs/light switches, shop door controllers and autonomous fans on grain bins. The system has been worth every penny, it’s detected 2 wet floors and one freezer failure, one furnace failure, the freezer had almost a full beef in it.
I don’t usually praise a product but this system has been excellent, simple to setup, in short it just works. It’s more than you need for monitoring a freezer but if you ever want to branch out your monitoring it’s an inexpensive place to start. There are other systems that are similar, pick one that has the most things you may use and go with it.
I bought my parents one for their house, I can monitor their freezers and house when they are gone.
https://www.amazon.ca/Wireless-Tempe...%2C391&sr=8-20