Confusion over applicationActivities in a UIViewController

I'm using this code to create a Share Sheet:

https://swiftui.gallery/uploads/code/ShareSheet.html

and I've got no problem bringing up a Share Sheet over another sheet. However, I'm having trouble getting it configured to share what I want. I'm trying to share a zip file out of my app. I've got an NSURL to the file I want to share, which I can pass with no problem, but it fails when I try to airdrop it. I assume this has something to do with applicationActivities?

Confusion over applicationActivities in a UIViewController
 
 
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