We have a rooted Android 8 phone that needs to act as a gateway to pass UDP packets between an external WiFi access point and the built-in cellular internet connection.
The WiFi access point generates UDP packets. The Android phone connects to the access point via WiFi. The android phone needs to be configured so that it passes the UDP packets from the Wifi adapter to the cellular modem so that it reaches the PC. The cellular SIM in the phone has a static IP address. When using a UDP test app, we are able to send packets from the phone to the PC and back without any problems. However for some reason the packets coming in from the WiFi access point are not routed properly to the cellular connection.
The project will be considered finished when you can demonstrate that the UDP packets are being routed from the access point to the cellular connection.
We have TeamViewer set up on the phone so you can remotely access it.