With iPadOS and iOS 13, Apple is finally adding much-requested support for external storage connectivity on iPhone and iPad.
During the WWDC keynote, Apple focused primarily on the use cases with iPad and iPadOS, but the iPhone [also works]. We had no issue connecting SD cards into our iPhone with Apple’s SD card to Lightning adapter and having them accessible within the Files app.
The iPad is really where external storage comes in handy. It is exceptionally powerful and full-featured. Not only can you connect SD cards and thumb drives but portable hard drives and solid state drives. Desktop hard drives also connected without issue.
MacDailyNews Take: So, as expected, iPhone power constraints preclude more power-hungry forms of storage such as external HDDs and SSDs.