Hostapd & dnsmasq

hi, networking noob here trying to figure out a few subtilities with dnsmasq and hostapd.

I got a system here with some sort of networking complexity :)

It has four LAN ports, a wifi card ( capable of doing AP), and an embedded cellular modem.

the cellular modem connects using a service/bash script and gets assigned new interface name once connected.

both wired LAN and cellular connection works fine, I can ping the net and access it independently.

I've successfully configured hostapd and dnsmasq, to share my internet connection from one of the LAN ports and can connect my cell phone on the wifi AP and it get internet access (but only from the LAN port), if I disconnect the LAN port (which is connected to my internet router) the cellular modem will not share it's internet on the AP.

from my understanding, dnsmasq will share / forward <internal> internet connection from whatever the source except for the wifi card. *which get excluded from the list in dnsmasq.conf (interface) configuration...

could it be that the rules are made just before the cellular modem gets connected?

I would also like to have one of the LAN ports to provide DHCP and share the internet from either LAN(from the router) or the Cellular modem.