Wireless Joint

It's likely that the orbi and its EG18 is not dealing out an IPV6 only interface that is 1pv4 over ipv6 (CLAT/XLAT) enabled. The latest Tmobile network structure is pushing hard to IPV6 only, and most legacy devices can only use IPV4.

I've not tested my new Tmo SIM from Calyx in the Orbi, but I'll ...

This is a tough one. So many variables. Likely the issue is a firewall issue not allowing the nest products to ping the home server, or vice versa, via IPV4 or IPV6 (ICMPv6). VPN services do not use IPv6, so that is likely the fail there if it has to be transmitted over IPv6.

The latest routers use ...