Support IPV6 when using Tmobile/Verizon 5G home internet
I believe the only way to get IPV6 addresses to LAN clients with these providers is to put the Eero in bridge mode. At which point one looses SQM, data usage monitoring and automatic channel selection. I realize that Verizon/TMobile are only issuing a /64 to their router, and so a second downstream router is a problem, but there must be some way to workaround this. Unfortunately I'm not enough of an IPV6 expert to comment in more detail - and the point of Eero is it should "just work".
I debugged this in some detail. The Verizon 5G home gateway does not supply DHCPv6 on its LAN interface, in either "default router" or "IP passthrough" mode. I believe this to be the problem. A downstream routes needs to be told it is using a cellular network WAN, and would need to implement something like RFC7278 an extract the /64 prefix and the DNS from the Router Advertisements packets transmitted by the 5G gateway on its LAN interface. Internally the 5G gateway will be doing this itself. See https://lkhill.com/ipv6-based-wi-fi-hotspots/ and an introduction to this. Another vendors router I have has the same issue, but their permitted me ssh access and I was able to debug it using tcpdump.