This script uses ModemManager to automaticaly setup a Huawei 4G modem internet connection by monitoring autoplug events from ModemManager, setting APN on new modem detection and then letting systemd-networkd to obtain the ip address for the modem interface.
You need Python 3 with python-systemd, python-gobject, python-dbus libraries
On the system side you have to install and enable ModemManager service and also
systemd-networkd and systemd-resolved. Sample config files that i used are
provided in *.network files