I've seen many DIY ventilation systems for the Elegoo Saturn 2 printer, but I wanted a part to attach a 120mm fan directly onto the ventilation hole of the UV Cover.

You can then print a 120mm to duct adapter (depending on your duct dimension) to attach to the other side of the fan.

In the pictures I am using a 120mm to 3"/80mm duct flange, you can find it here https://www.thingiverse.com/thing:4221712

My part has builtin holes for threaded inserts (M2) so you can use some M2 screws to fix it to the UV cover. 

EDIT 09/05/2024: Added a new version with larger holes for M3 threaded inserts, so you can use the provided screws used with the red cover