Hello,
we don’t have such a guide yet.
The idea is to use network-manager.
You’ll need 2 files in the system-connections folder of the boot partition of your device image.
- one will be for the wifi hotspot, similar to what you’ve seen in this thread or in Raspberry-Pi Wifi Access-point
- the other will be for the 4G connection
If you run a Linux distribution using NetworkManager, you can try configuring your 4G modem and wifi hotspot using the graphical interface and then look at the files it created in /etc/NetworkManager/system-connections/