While highly desirable for many applications, this plays havoc with redundancy if Ignition clients can connect through either network.
The only good solution I'm aware of is to have DNS on all networks resolve names for these gateways, in such a way that the IP returned for your gateway to a client is the correct address for that client's network.
Then the Public HTTP Address setting that Kevin points out can be set to the domain name and all of your clients will "just work" using that name.
{FWIW, the setting in dnsmasq for the desired response behavior is called "localize queries".}