How to Decouple iCloud-Sourced Photos from the iCloud in Photos Application Is there a way to decouple photos from iCloud in the Photos application when they arrive?  Basically, on macOS, I would like iCloud to deliver new photos and otherwise leave my local photo library alone.  If this is not possible, is there a work around, such as a method for creating independent copies of photos that arrive via iCloud? 

I have found similar questions that explain that iCloud tightly couples photos across devices but nothing about how to work around the problem.  Clearly different devices have different storage capacity, so it makes sense that one would like to enforce different policies on each device.
You cannot in Photos designate some photos as "local" and others as "iCloud Photo Library". It is all or nothing.

However, you can have locally stored photos outside of the Photos application, which will be untouched by iCloud Photo Library.

Regarding your comment about storage capacities: In Photos Preferences under the iCloud tab, you can set your storage policy to either (a) store photos and videos in full resolutions on this Mac, or (b) store photos and videos in full resolution on iCloud primarily and only cache photos/videos in full resolution locally as available storage allows.