I've been working on this today. I got both the LG and the Pantech devices in today.
The LG device is unresponsive. It does not give any responses to any commands on the tty port (and I tried turning echo on via ATE). Trying to bring up the ethernet interface only switches it to unknown state.
The Pantech device is responds to commands. I accedentally clobbered the pdp 1 context by trying an APN before first checking to see what it was set for. There were two other PDP contexts already configured as follows
Originally, I was able to get it to connect to the vzwinternet context. pppd showed a successful authentication but then did not get any ip address or gateway.
On Windows, the LG device was able to connect using CDMA but not LTE. The Pantech device was able to connect to LTE and got 16Mb downlink and 0.9Mb uplink. My next avenue will be to use a USB analyzer to find what the Windows software is doing.