I have verified it is not my external IP. So I guess what remains might be the IP assigned to my “modem” by my ISP? Which begs the question, why do you not show the external IP?
I know all my other routers have done so ( Asus, Mikrotik,Ubiquiti ) , as far as I can recall.
The modem from your ISP is in Router mode, which means it has your public IP going into the modem/router and gives you a private IP address for your red interface.
That is correct but it is your RED interface IP.
The only way for IPFire to find out what your Public IP from your ISP is would be for it to send messages out to some server on the internet and use that to send back the Public IP.
IPFire does not send out messages to places on the Internet where you don’t know what it is doing.
If Red did find out what the Public IP was and showed it there then people might think that they should use that IP when creating a Port Forward rule, but in fact you would need to use the private IP given to you by your modem. Additionally you would need to add a Port Forward to your modem/router as you have a double NAT situation.
I would want to know on that home page what IP my Red interface actually has, not the IP of my modem if I had one.
The only place that IPFire does use an external server to find an IP is on the Dynamic DNS page where if IPFire is behind a router you can find the Public IP by contacting an external server but it is a choice that can be made by the user, whether to use that or not.
I would suggest that you should look at the possibility of changing your modem mode from router to bridged. Most modems allow you to do that. With this mode the modem then passes straight through the Public IP and your Red interface will show that IP. Also any Port Forward rules will only have to be created in IPFire.