Isadora and OSC works fine on multiple network interfaces

Here is an example config with the ethernet interface at 192.168.1.1  and a Wi-Fi interface at 10.0.0.50

A sender device ( eg. TD or qlab) interface is 192.168.1.2. In the application preferences, set OSC address (host, or destination or listener or udp -meaning isadora here) to  192.168.1.1  

A listener, ATEM mini is on the same LAN at 192.168.1.3:3333 - Here, adjust Isadora's OSC Transmit actor to match ATEM's device address. 

A wireless control device (touch OSC/phone) at 10.0.0.22. Isadora is on the 10.0.0.50 interface there so my phone's TouchOSC prefs need to be set to send to Isadora at 10.0.0.50

192.168.1.255 can also be used to broadcast the values to all devices in the 192.168.1.xxx network. Similarly, 10.0.0.255 will broadcast to all devices on the 10.0.0.xxx network.

 Here is an example of using OSC over two interfaces.  on the listener /Chan1 is a from a PC with no wifi. just a direct cable with static IP  TD. 

The /3/xyM+i coming from my phone over the home WI-FI

If you want devices on different networks to communicate to each other then you need to consolidate the network so they are on the same network, but that's an IT solution.  Nevertheless, Isadora can overcome that if you use it as a pass through. It's a good way if you want to limit ranges and have conditions or rename the address of the values to be forwarded.