Support
Saving does nothing, or says Photos access is off.
Open Settings, then Twofold, then Photos, and choose Add Photos Only. Then tap Save again.
How do I set the wallpaper?
Which inner size should I use, Wide or Upright?
Wide (2670 x 1878) suits the open, landscape book pose. Upright (1878 x 2670) suits the inner display held in portrait. You can save both.
Still stuck? Open a support request (a free GitHub account is needed). We reply there.