Mobile Carriers in the United States

[dukla2000]

I found it, but it's grayed out for me. 

Yeah that is same for me, it it temperamental! if you exit WiFi settings, go back exit, check Bluetooth etc eventually you should find it selectable 

So you're right on both counts. It was grayed out, but switching into other menus eventually made it clickable. When I enabled it, it behaved exactly as you anticipated; showed up just long enough to try to connect before cutting out and searching for known networks.

...

Working pretty well now, at least with Debian/phosh.