OK, so perhaps it's time to post something about what Apple’s Advanced Data Protection is, what it does, and why it's inaccurate to say that Apple is "removing iCloud end-to-end encryption". Bear in mind I am simplifying, but only slightly and mainly so I don't have to write a 3000 word essay.
There are three kinds of encryption which often get conflated. In-transit encryption in its classic sense is simply encrypting something at the senders end, and decrypting it at the intended receiver. It basically stops your message or file being read in transit. It's also sometimes used to mean it must also be stored in an encrypted form at the receivers end. This ain’t necessarily so: and it doesn't always mean the file can't be read, either.
Encryption-at-rest means that the files at the receivers' end are definitely stored in an encrypted format. This means that only you, and the company that provides the storage, hold keys which can decrypt those files.
Zero-access or zero-knowledge encryption takes this a step further, by removing the ability for the service provider to decrypt the files. Effectively, only you hold a decryption key. The company itself can never read your data.
Zero-access is sometimes called end-to-end encryption (including by Apple) reflecting that files are encrypted and inaccessible to anyone unauthorised at every step of the way. However, you'll also see end-to-end meaning in-transit, particularly in older documents. Hence, I try and avoid the phrase entirely.
Why is this important from a privacy/security standpoint? Because many governments around the world can, and do, have laws on the books which allow courts to order a service provider to give them access to your files in a decrypted form. If the company holds a decryption key - which it always does with anything less than zero-access systems - it can always give law enforcement your files.
Google Drive, Dropbox, OneDrive, and the "standard" iCloud all use both end-to-end encryption where files are encrypted-at-rest. No one can access your files, except you, people at the company who have access to decryption keys (this is always a very small number of people for obvious reasons) and law enforcement/spooks with the right paperwork.
Apple's Advanced Data Protection system, which was introduced in 2022, optionally allowed a user to switch to zero-access encryption for most iCloud services. This placed it above Google et al in terms of security and privacy. Most iCloud users have never turned it on. It's mostly people like me, who might have a need for higher levels of security, who did.
Governments generally hate zero-access encryption, because it stops them being able to get to data without the person they are monitoring knowing about it. Without it, they can simply get a secret court order which allows them ongoing access, and to be fair to them that is understandable when you're dealing with serious, ongoing crime, from drug smuggling to child abuse to large-scale cybercrime.
But although it's understandable, it's also dangerous. And the UK law is particularly bad, as it purports to allow the government access to to any account not just in the UK, but anywhere. This means, for example, that the UK could gain access to a US account, and pass that information on to the US government -- effectively circumventing US legal protections on surveillance.
So what's happening here? First, we don't yet have all the details. What we do know is that ADP will no longer be available in the UK. The most likely outcome is that UK users will effectively drop down to the "standard" level of security. That means files will be encrypted end-to-end, and at-rest, but not zero-access. Apple will hold a decryption key which will allow it to respond to any court orders for data access, as it (and Google, and Microsoft, and Dropbox) can and does at the moment for anyone who hasn't turned on ADP.
How many people will this affect? Only Apple knows that, but it's fair to say that opting into ADP is probably not done by the majority of users. It's been fairly hidden, and turning it on does impose some restrictions which I suspect most "normal" users would find annoying. So, for most Apple users, nothing much is really changing.
And it's worth saying again: what Apple is offering is still as good as Google, Microsoft, etc, none of which offer zero-access encryption for file storage. There are remarkably few companies that do: the only one I've come across is Proton, whose Proton Drive is hosted in Switzerland, subject to Swiss privacy laws, and zero-access encrypted by default. If you’re currently using Advanced Data Protection for file storage, they are worth a look.
Whoops. This turned into an essay. Ah well.