Why is a question about setting up a PHP framework using a PHP package manager off-topic for Stack Overflow?
Is there a Stack Exchange site where this question would be considered on-topic?
This isn't off topic for Stack Overflow.
The last revision of the question before it was closed doesn't tell me anything about the question that would put it outside the topical scope.
The original question would probably have been closed as not a real question, but you put in substantial effort into making it a real question that seems to me that it can stay open as such, plus you did so many hours before it even got closed. But I just don't see how your question could have ever been "off topic", especially considering the reasons you state here.