“The networkQuality tool is a built-in tool released in macOS Monterey that can help diagnose network issues and measure network performance.”
One Terminal command runs a speed test that also rates responsiveness in round trips per minute. The sample run shows 162 Mbps down and a Low responsiveness score of 73 RPM. Every run also fetches its config and test servers from Apple. Fast pipe, sluggish line, and the usual speed test only reports the first number.