PhotoKit - non-system library

I have the same question. My motivation is testing: I’d like to write an app against PhotoKit, and I’ve been thinking about how I’d test the app. I’d need to test different cases with different “states” of the library. I suppose I could add/remove assets to/from the shared library to get it into the expected “before” state for each test, but that would preclude running my tests concurrently.

Is there any way to create and work with alternate photo libraries programmatically? Ideally, concurrently?

Same, I was wondering if it's possible to load and manage a photo library (basically a non-System Photo Library) by passing a file path URL. Based on the lack of responses, seems like there's no way to do this.

There is no supported way to use PhotoKit with Photo Libraries other than the System Photo Library. I'd recommend filing feedbacks detailing your specific use case and workflow that you're trying to accomplish.