Since you seem to be the maintainer of the qmi_wwan driver (lucky me 
), i submitted my first linux patch to you (and the other maintainers). Hope it makes its way into linux sometime... Thanks again for your help!
at the same time i also patched the usb option driver to support the ttyUSB for the modem...
I'll just post here to avoid spamming the github PR: So there is a micro USB connector on this device, but the data lines are not connected to MT7620? (iirc it only has one USB phy, which connects to the modem) but they do go into those 0 ohm resistors? Is it used for powering the device, or what would happen if you connect it to a host?
Some devices use the cdc ethernet gadget-mode kernel driver to emulate a usb ethernet device (would require a usb phy though), some have a dedicated usb-ethernet chip and connect to the switch, but I haven't seen any on the pcb. Although there is an additional option for a type B connector, but those data lines go to some controller that is not populated... maybe the same as for the micro USB port? Some USB switch maybe?
// edit: okay I see the bq24133 at U11 is a Li-Ion battery charging controller from TI. Does this thing have a battery, or just the Zyxel version?
// edit #2: P1 is probably for an RJ11 connector rather than USB, and the IC footprint looks different to bq24133 (pins on all 4 sides)