Activity view for All Photos disappears instantly

Here’s an odd one that I’m curious if anyone else has seen. Whenever I tap a button that tries to bring up an activity view showing all my photos in an iPhone app (like All Photos when picking a photo in Messages > ••• > Edit Name and Photo, when trying to attach a photo in Gmail, or when uploading a photo to a Google Form in Safari), the activity view flashes briefly and then disappears. I had thought it was specific to Safari before, but I just hit it in Messages and Gmail too.

iOS 13.1.3 on an iPhone 11 Pro. Restarting the iPhone had no effect. I really don’t want to try turning off iCloud Photos, although I fear that’s in my future. Any ideas?