It’s possible to get it working only using LNS, which is easier if maybe a little less stable in the O(5 years) timeframe.
I followed the instructions in the Laird App Note here. There’s a bug in the instructions though, and then another bug which compounds it:
It says
For Unix based OS - “\r” must be added to end of key for proper line endings
but then gives the command
Echo -e "Authorization: Bearer NNSXS.xxxxx\n">tc.key
Which is wrong. Do what it says, not what it did. The correct command is:
echo -e "Authorization: Bearer NNSXS.xxxxx\r">tc.key
The second bug is that if you upload a key file with the same name it doesn’t seem to stick – rename it to tc2.key and upload it and it’ll be fine. And it’ll go to the configured band plan and not the one hardcoded on the device (important for RG191s sold into other countries prior to this hard-setting and country-specific versioning).
If you do this key file incorrectly there is an error in the log (bottom lines, turn on auto-updating) saying the key file is in the wrong format but it wasn’t updating the first time I uploaded everything (and in fact locked itself into online state but didn’t do anything). Rebooting helped.