Comment by concinds

iCloud E2EE ("Advanced Data Protection") is far from perfect:

- hashes of files and photos are not E2E encrypted even with ADP on, and are accessible by Apple, "so Apple can perform deduplication". It also means they still know if you have a given photo in your photo roll.

- file type, file size, modifid/created timestamps (Photos/Drive) are not E2E encrypted even with ADP on, and are accessible by Apple

Apple says these are due to technical limitations and they're working on it, but be aware of these limitations.