The version on the bottom of the deco is 2.6, though that wasn't an option for the hardware version.

When trying to add a port forwarding rule via the app->home->more->Advanced->NAT Forwarding->Port Forwarding->+, I enter all the required information, however, when I'm finished and click Save I see the message, "Adding this entry will assign a fixed IP address to this device and clear the IP address you reserved for this device before.  Add now?", which is confusing, what is meant by "this device"?  The deco or the client ip address I'm trying to port foward to, I think it means the deco xe75.  Regardless, I clicked OK and it fails to save the port foward and just displays the same blank page with no ports forwarded.  I made a guess that perhaps the deco XE75 needs a static ip address (as it was getting it's IP from my ISP router, though that IP was reserved so it would remain the same, went back to home->more->Internet Connection and changed from Dynamic IP to Static IP, entered in the same information that was there for the Dynamic IP, clicked Save and retried the above.  I still get the same message, "Adding this entry will assign a fixed IP address to this device and clear the IP address you reserved for this device before.  Add now?", however, now it actually adds the port forwarding rule.

In my opinion, a better message would be "This router must be configured to use a Static IP address, instead of a Dynamic IP.  To accomplish this go to the Internet Connection under More and change the Internet Connection Type to Static IP and ensure, if you have this router connected to your ISP's router, that that address is reserved."  It's a bit wordy, but still better than the current message, at least for me.