This is a this-to-that conversion. It attaches to the gutter and funnels the rainwater into a 3/4" pvc pipe to capture rainfall on the greenhouse and move it to water catchment barrels.
It converts from this Home Depot vinyl gutter type to 3/4" pvc pipe.
https://www.homedepot.com/p/Amerimax-Home-Products-White-Vinyl-K-Style-Drop-Outlet-M0506/100063571
You can also use the OpenSCAD script to make your own this-to-that. The script can easily be modified for any size square to circular funnel conversion.
Best printed with the 3/4" pipe end facing the bed and a 10mm brim.
The author marked this model as their own original creation.