Most technical subdomains run by Amazon are fully operational endpoints — APIs, scanning tools, or administrative dashboards. This one, qagpublic.amzn03.scan.amazon-corp.com, returns a 404 error instead of any actual content. That makes it impossible to evaluate for safety in any real sense.
There are no obvious signs that this is a phishing or malicious site. It's hosted on Amazon's own network and uses a certificate issued by Amazon. But the fact that it doesn't load anything means there's no service to use, no data to trust, and no reason to treat it as a working site.
If you came across this URL expecting a tool or a page, double-check the full address. It might be a test endpoint that's no longer active, or a typo. Either way, don't rely on it for anything — there's nothing there.