As I continue on my Sailfish/Gemini journey, I finally got LTE data working in the USA on the Verizon network.
With that now working, I discovered a new Sailfish bug: When the device switched the network default route between LTE to WiFi, the default route disappears from the routing table,
as observed via shell executed netstat -r. I need to reboot to get the network stack working again, or manually add a default route back in as su-devel:
route add default gw 192.168.11.1 wlan0
for example to get things working again with my inhouse WiFi.
Also, I can receive phone calls while registered on LTE, but after the call, Sailfish compains that no SIM is inserted until I reboot.
I am still learning my way around this OS, so I don't think I can be much help yet.