Good point, ppp is not enabled! Option seems to be --enable-ppp. I'll try it. This NDISDUP seemp pretty problematic. In fact I found MM patch whose introduction comment describes pretty much how this modem works (https://cgit.freedesktop.org/ModemManager/ModemManager/log/?h=dcbw/huawei-at-dhcp). I'll check if that helps/works with this MM version - then I suppose, I should contact MM mailing list...