This is a front plate or a mount for the Home Assistant Yellow for the Blinkinlabs 19cm Mini Server Rack.
It uses the two front screws from the bottom of the Yellow.
The hole to the right is for the cables if you decided to route them to the back. There's a cable tie point right behind it.
After you print it, it only feels flimsy without the HA mounted. Screw it in and the whole thing stiffens up.
The author marked this model as their own original creation.