This is to hold the Xiaomi temperature/humidity sensor with a display.
Auto generated tree supports may be nice for the small tabs and the breather holes.
Guide to convert it from Bluetooth to Zigbee:
https://smarthomescene.com/guides/convert-xiaomi-lywsd03mmc-from-bluetooth-to-zigbee/
(Not my guide, all credit to original creator)
The author marked this model as their own original creation.