e2ee for iCloud is currently opt-in, without prompts/nudging. Most power users don't even have it turned on or are aware of its existence. The setting is buried/hidden in submenus.

Approximately no one uses it.

Hopefully Apple will begin promoting users to migrate in future updates.

Indeed. After looking at the documentation, photos are not e2ee by default.

https://support.apple.com/en-us/HT202303

> Most power users […] or are [not] aware of its existence.

Anyone who doesn't know about this feature is not a power user in my book.

It only just came out this year and it comes with some pretty serious UX issues around potentially getting locked out of your data.

> The setting is buried/hidden in submenus.

Mind sharing where it is on an iPhone and Mac? I have not been able to find it.

How to turn on Advanced Data Protection for iCloud

https://support.apple.com/en-gb/HT212520

It's called "Advanced Data Protection for iCloud"

It's kinda complicated to turn on, as it disables most account recovery options.

It was announced some time ago, but remember that you need modern devices on both sides to enable that feature.