Huh. I'm pretty sure that was largely obsoleted a while back (like, over a decade probably, not too long after this was written) by NetworkManager and ModemMana

Huh. I'm pretty sure that was largely obsoleted a while back (like, over a decade probably, not too long after this was written) by NetworkManager and ModemManager adding better handling for all the weird quirks that did actually matter with mobile broadband. It might still be possible to use it with the right manual configuration and additional software, but it'd mean dealing with badly documented quirks that are just handled for you by ModemManager.