This is a simple mount that can be attached to one of the extruded profiles on the Prusa MINI+ (and possibly other extruded profiles that match its dimensions).
It is designed to fit a DHT22 module such as the one found here: https://www.aliexpress.com/item/32802908424.html. If the link is not valid anymore, have a look at the pictures for reference. Once the mount is in position (inserted and rotated 90°), the friction fit should make it fairly stable.
There is a little lip around the mount to allow some space for some of the components on the board that may protrude on the underside of the sensor board. The holes are slightly undersizes and can accept M3 screws.
The author hasn't provided the model origin yet.