So sorry to hear about all these issues. For the modem, can it be assumed that you've opened up the back and checked the DIP switches? One of them is for the modem.
As for the libgpiod1 and libgpiod issue, you might look at this thread. The OP solved the issue, but found another one:
https://forum.manjaro.org/t/oudated-syst...ies/158764
As for the libgpiod1 and libgpiod issue, you might look at this thread. The OP solved the issue, but found another one:
https://forum.manjaro.org/t/oudated-syst...ies/158764