Duplicates Monitor is a menu bar app of Gemini 2 that prevents cluttering of your Mac and ensures no copy is created unnoticed.
When you open Gemini 2.8.0 or higher for the first time, Duplicates Monitor is launched too. It starts watching the folders you’ve just cleaned from duplicates and alerts you as soon as a new copy is detected. For example, you can be immediately notified if you've downloaded the same report or song again. All you need to do is add the Downloads folder to Duplicates Monitor and keep it running.
Have a quick look at Duplicates Monitor and its capabilities: