4G USB modem with Armbian

Not much of a tutorial, but it is something that often needs some googling and head scratching.  This is how I got my particular modem working, your mileage may vary.

Step 1)  Get a modem that will work.  I got a Huawei E397u LTE/UMTS/GSM modem.  It's Cricket branded, but I'm on Google Fi, it will work with my data SIM.

Step 2) Plug it in and see that it doesn't work.

Step 3a) apt update

Step 3b) apt upgrade

Step 4) Install usb-modeswitcher

Step 4, optional part 2) install modem-manager, modem-manager-gui  (for general playing around)

Step 5)  unplug/replug the USB modem, see that it should magically have a different VID:PID when you type lsusb.  You should also have some ttyUSB's, and you can check out modem details in the modem-manager-gui

Step 6) set up network connection via the network dropdown at the top right of the desktop.  You will need APN information for your carrier.

I put in modem-manager so I could debug.  It will cause issues if you do certain things with it while connected.

My modem was $15, Ebay has them. https://www.ebay.com/itm/BRAND-NEW-Unlocked-Cricket-Huawei-E397-E397u-53-4G-LTE-Mobile-Broadband-Modem/262898110276

So does amazon.