I have always backed up my iPhone through iTunes but I decided to use iCloud now as well. I only have the free iCloud plan with 5 GB of storage (of which 4.5+ GB free), and I'm attempting to backup an iPhone 7 with iOS 11.0.
I tried enabling iCloud backup but I got back the message: "This iPhone cannot be backed up because there is not enough iCloud storage available."
According to this fairly old Ask Different answer and this Apple support document, there should be a "Choose Data to Back Up" option to allow me to disable specific items to backup (e.g. camera roll which should be enough to allow my backup to proceed). Unfortunately I can't see this option when following the Apple support document's steps for iOS 11. When going into Settings -> my name -> iCloud -> Manage Storage -> Backup, this is the screen that shows up:
According to the support document I should now select the iPhone I want to backup, but as can be seen, there is no such option. I speculate this is because I never completed any backups at all. Thus I can't tick off items taking up lots of space to get the backup to complete for the first time.
How do I access the list of items to back up, so I can tick off some items to get the backup small enough to fit the available space?