Comment 8 for bug 1910550

@Jon, thanks for the logs. The modem is using the generic plugin, which does not have direct support for NCM. That implies that if you want NCM, probably a new plugin needs to be implemented.

It might be interesting though to see if the modem can use pppd to establish a connection. Could you please share journal for that case and check if connectivity works? Creating a connection can be done via NetworkManager, with a command like:

$ nmcli c add type gsm ifname ttyACM2 con-name <name> apn <operator_apn>

(see details on [1] - the doc applies to UC but most of it is valid for classic too).

Also, if in the end you do not care about NCM/MBIM, you could try the latter to check if that works out of the box for you. I have seen in the AT commands manual from Sierra that you can switch to MBIM mode with
AT+KUSBCOMP=2
(after that probably you will need to reset the modem)

To go back to NCM after your testing:
AT+KUSBCOMP=0

Some other questions I have:
1. Which version of Ubuntu and ModemManager are you testing with?
2. The docs have different instructions for Verizon and rest of carriers, which carrier is this for?

[1] https://core.docs.ubuntu.com/en/stacks/network/network-manager/docs/configure-cellular-connections