A few years ago, there were 3 tools for diagnosing network problems: Network Utility (gone in Big Sur), Wireless Diagnostics, and Network Diagnostics (also gone). And what can networkQuality tell you about Private Relay?
Network Diagnostic
If you want to check out your Mac’s Wi-Fi connection, Wireless Diagnostics is ideal. It’ll show you signal dropouts and give its opinion.
How can I investigate frequent errors when browsing of “Can’t find the server”?
The Eclectic Light Company 