Among the most useful are Archive Utility, now including Apple Archive compression, and Storage Management. But Network Utility is now non-functional.
Apple asks us to report all bugs through Feedback, a system which it controls, and uses to its own advantage. Doing so discourages Apple from thoroughly testing its products, and we’re the losers.
What should you do if you think you’ve found a security vulnerability in macOS, or an app provided by the App Store? Will you get a bounty?