Port forwarding on Quectel EG912Y-EU

Great, then try

AT+QCFG="nat",1
at+qicsgp=1,1,"your APN"
at+qnetdevctl=1,1,1
AT^RESET

and check your host wwan0 IP - when the modem is in network card mode the host should receive the address from the carrier and not from the modem like it was before. With NAT eliminated your host should be now reachable within your private network.