Simple-Comic: QuickLook doesn't work

Ah, there we go, that’s the reason then. Good news and bad news:

Good: You can easily fix it by running the xattr command again, but with the parameters set to remove the attribute: xattr -r -d com.apple.quarantine path Afterwards QuickLook should work, though I’m not sure if you need to run it just on the QuickLook plugin inside the app, just on the app, or on both.

Bad: I have no idea why in your case the attribute was present and it was not in my case. That attribute is set by macOS on downloaded applications, and it’s the reason for that warning popup when you first open such applications. However, QuickLook plugins are not able to trigger that popup and thus just don’t run when they have the attribute.

I’m not sure if it is macOS or just Safari that is setting the attribute, so maybe downloading the application via e.g. Chrome would have a different result. But I used Safari, and I didn’t have the attribute set. You did run the app once before trying QuickLook? Another difference I could think of: I’m using BetterZip instead of the included Archive Utility. Maybe upon extracting the downloaded ZIP file, BetterZip drops the attribute, while Archive Utility preserves it?