Airport Extreme won't work: "Cannot be setup by this software"

Solution 1:

You can actually get this old piece of technology to work fairly well with a few easy steps.

1. Power off the Airport Extreme and any other router it is connected to for 20 seconds.
2. Turn everything back on and wait for lights to stop flashing.
3. On your iPhone go to Settings > Wi-Fi. Turn on the setting for Ask to Join Networks. This will make it so the phone always asks you before joining an unknown wireless network.
4. Now go to Settings > General > Software Update. You will be prompted to Select a Wireless Network with the Apple Network abcdef as an option. Touch it.
5. You should now be connected! There is no need to actually perform the rest of the software update at this time.

I think this works because - one, the software update tool really wants you to download (very large) iOS updates on Wi-Fi to save your data. And two, the Airport extreme for some reason only works if you ask to join the network such that the network selector will pop up. It's a hack, but it works!