IPhone photos still stuck on “Restoring from iCloud”

This is most likely the carrier intentionally deactivating the old SIM.

When iPhones first came out, your current phone would normally get deactivated at the moment you purchased a new phone and told the carriers to move the service to the new phone. Now, they wait until the new phone checks in to perform the swap to account for delivery delays, backups, etc...

Your first step should be to contact the carrier and explain that you want service on both phones and arrange for which number rings to which device. They might be able to accommodate this over the phone, but if the old SIM has been deactivated in the networks, most carriers are very unwilling (or unable) to re-activate the old SIM and instead ask you to get a new SIM from them at a convenient local retail spot or by them shipping you new SIM card(s).

Apple's restore process and activation of the device doesn't affect network activation and for locked phones, you just need a SIM for the correct carrier to activate the device. iOS does not check or care that the contract is expired, not established or live for iOS activation - just that the SIM is manufactured for the correct carrier.

Turns out I solved the issue by just wiping my phone and restoring it from that same Sept 27 iCloud backup again. It had the photos in the backup after all. As to why it didn't download them to my phone when I restored from that backup a month ago, I'll probably never know.

Before I actually wiped/restored, I wanted to make sure that the backup actually had the photos in it. Of course Apple doesn't let you see the data in your backups, so I had to download a 3rd party backup viewer on my mac to look at the pictures in the backup file. Once I saw the photos were really there in iCloud, I decided to just restore from that backup and see what happens. It ended up working. Weird.