When attempting to add an existing photo to a message in the Messages app, the grid of available photos cannot be located or navigated by swiping, only by touch

1. Ensure that VoiceOver is enabled.
2. Open the Messages app.
3. Double tap with 1-finger on the “Compose” button.
4. Locate and double tap with 1-finger on the “photos” button (double tap first on the “Apps” button if available apps are currently hidden).

At this point a grid of photos should be displayed in the bottom quarter of the screen.

5. Swipe right/left with 1-finger repeatedly to locate all UI elements on the screen.

You should find that VoiceOver does not locate the grid of photos.

You can, however, locate by touch the grid of photos. Having located a photo by touch, you cannot move through all available photos by swiping right or left. When you do swipe, VoiceOver focus will move to either the UI element that precedes or follows the grid of photos.

This behaved as expected in iOS 14.x, and there were buttons that allowed you to toggle between recently taken photos and all photos. If those controls are still available, it does not appear to be possible to locate them with VoiceOver enabled - either by touch or swiping.