This is very Apple specific, which makes it kinda off-topic for Swift Forums, where the focus is on the Swift language and related open source technologies. Please start a new thread over on Apple Developer Forums. Tag it with (at least) App Sandbox so that I see it.
However, just to set expectations: I don’t think you’ll be able to make this work. Quick Look extensions, in common with all app extensions, must be sandboxed. And that EPERM is a strong indication that the the Quick Look extension’s sandbox is preventing you from starting a child process.
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Quinn “The Eskimo!” @ DTS @ Apple