I am frustrated, trying to change from iPhone Xs 256GB to iPhone 12 128G so I must delete some of the pictures from the XS..
It is such an annoying process with Apple to download the pictures and delete the pictures if you are not using the iCloud option.
The Photos app is designed to cloud storage, so there is no traditional option to download the pictures as files, it is downloading them as library which is not visible to the regular user and can be managed only to what Apple think the end user should use.
The other alternative is to use Image Capture app which allows to download the pictures as regular files but there is no option to delete automatically after import (Apple invest the minimum on this app)....and now there is no option to delete all pictures at once...
Apple, why to complicate everything, pay Premium price on Apple devices and then struggle with the process :-(