Earlier quoted context omitted.
Same with Google Wifi and Google Home Nest. Also, fun fact, during an internet outage some time ago I learned that your Google Wifi can't even route locally if you don't have a live connection to the internet. That is, my Desktop could not connect to my NAS -- both wired via Ethernet to my Google Wifi network -- because there was no Internet access. This is a "feature", and is working as intended: https://twitter.com…
Disclosure: I used to work for Google and still work for Alphabet. That response is a little confusing: the management app is Internet only, but it doesn't drop all its routing tables or something just because the uplink is gone. Moreover, the regular DHCP and so on will operate just fine while not connected to the internet. I don't know what happened in your case and I totally agree that it's a bad experience for tr…
Luckily I had a ~15 year old Cisco router I could temporarily replace it with.