If you want to invest in Zigbee (low power sensors, buttons, remotes) you can get commercial products like Xiaomi Aqara, IKEA TRADFRI, Tuya or you can get a USB Zigbee stick (CC2531) and link all of the above through Home Assistant or NodeRED. There is a catch, you will need to flash the stick with custom software. It’s easier now as CC2531 at the ITEAD store comes pre-flashed for you. And you are correct, ITEAD are the guys behind Sonoff devices.
Why buy CC2531 at the ITEAD store?
You can get CC2531 for about $3-4 on AliExpress, so why would I advise you to use ITEAD store? You can follow this CC2531 flash guide, and flash it yourself without an expenisve ($10 for a single-use cable is a lot) CC Debugger cable, but despite my best intentions, I got a flooded with questions and issues associated with the process.
The one thing all these problems had in common was CC2531 v1.0 board. My tutorial was created for CC2531 v2.4 (the board I have) but there is no way of telling which revision will you get from China. Some people used the same link I used to get my USB Zigbee stick and still got the v1.0.
Instead of playing roulette, open ITEAD store and grab the CC2531 which is not only v2.4 but comes with pre-flashed CC2531ZNP-Prod firmware. Less risk involved, and all you have to do is plug it in and run Zigbee2MQTT installation instructions.
I have not been paid to promote the ITEAD store. I have seen other listings that will ship a flashed CC2531, but their prices were about $10-15 per USB dongle. CC2531 at the ITEAD store costs $3.99. It’s a no brainer. If you already have cc2531 – well I hope that my CC2531 Flash Guide helps! Let me know in this Reddit Thread if it does.