Can I connect the IXrouter3 to 2 different networks? One for internet access and the other for local communication to or from the machine? Similar to how the OT port works on the SecureEdge / SecureEdge Pro?

The IXrouter3 has no separate port for this. However, you can set it up to work in a similar manner by using a different feature: failover.

By configuring a fallback connection (failover), you enable an interface that you can connect to your OT network. The fallback interface will be active, even when the IXrouter3 is not actively using it to (try to) connect to the IXON Cloud. 

1. Configure one connection type (e.g. Wi-Fi) to connect to the network that provides internet access.
2. Then configure another connection type (e.g. Wired) to connect to the other network, the OT network.
3. Make sure that at Internet priority, the preferred connection is the one with internet access.
4. Proceed with configuring the IXrouter3's firewall accordingly. Depending on your use case, that can be Allow access from LAN to corporate network or internet , Set up 1:1 NAT from WAN to LAN , or Set up port forwarding from WAN to LAN.