Network Utility has been deprecated in macOS Big Sur, and its functionality can be replicated with Terminal commands.
For Wi-Fi issues, Apple recommends using the Wireless Diagnostics app.
The app had been hidden under System > Library > CoreServices > Applications since macOS Mojave.
Since the release of macOS Mojave, the app had been rather hidden under System > Library > CoreServices > Applications.
Network Utility's functionality can still be replicated with Terminal commands, and for Wi-Fi issues, Apple says to use the Wireless Diagnostics app.
Network Utility Deprecated in macOS Big Sur - MacRumors
With Network Utility X you can quickly find all informations about your network. ... than 100k downloads on iOS platforms, Network Utility comes also to macOS ...
Network Kit - macOS | DoubleREW
All apps in the network-utility category. ... 2 Pingnoo 9 alternatives to Pingnoo Pingnoo is an open-source Windows, macOS and Linux visual trace route ...
Network Tools for Mac | AlternativeTo
Download Network Utility and enjoy it on your iPhone, iPad, and iPod touch. ... App Store as Network Kit X, the same app but tuned to take advantage of macOS. ...
Network Utility on the App Store