ModemManager ============ Important notice ---------------- If you are using a mobile device with integrated WWAN module, a manual configuration step is needed after installing or upgrading modemmanager, otherwise the module might NOT be useable anymore. Unfortunately, the logged error message will be slightly misleading. So, if you see a message like [modem0] couldn't enable interface: 'Invalid transition' in your system logs or ModemManager keeps enabling and disabling the module every second, you are probably affected by this change: Starting with release 1.18.4, ModemManager does no longer enable the automatic FCC unlock for certain types of modems by default. THIS MAY BREAK EXISTING SETUPS You can restore the old behaviour AT YOUR OWN RISK by creating symlinks in /etc/ModemManager/fcc-unlock.d: sudo ln -sft /etc/ModemManager/fcc-unlock.d /usr/share/ModemManager/fcc-unlock.available.d/* See https://modemmanager.org/docs/modemmanager/fcc-unlock/ for details.