Couldn't almost any WiFi router, and thus the user of that router, then be in violation of GDPR simply by logging which MAC addresses attempt to connect to that router? Even connections by accident (selecting the wrong SSID).

I know my Netgear router has a history of basically any connection attempts and their MAC address; it does this by default, not sure I can even turn it off.

And how would you even present a GDPR notice to the user prior to logging that kind of information?