Hello Max Hug,

From Google:

Before you begin, you need to install the Google Wifi app on an Android or iOS device. The app is the only way to access the device’s settings — it’s not even possible on a computer. (And, of course, you’ll need a Google account to sign into the app.

The only free software that comes to mind for troubleshooting network issues with residential hardware is Wireshark.

Wireshark for beginners