For a dial up modem on a serial port, install pppsetup.tcz and all dependencies, and dependencies of dependencies.
If you install pppsetup.tcz using the App Browser, you will get them.
It can be set up just by running ppp-configure from the menu, or sudo pppsetup from the terminal, and answering the questions correctly.
Callback - answer no.
Don't change the default modem string.
Leave Internet Service Providers Domain Name blank.
You don't need to modify files afterwards, like they do with 3g modems.
After setup, the following files need to be included in backup, or made into a new extension.
etc/ppp
etc/resolv.conf
usr/local/sbin/ppp-go