If they do close an account they have a support line you can call and talk to a human.

For what it's worth, Apple closed my mom's account due to inactivity. (She hadn't used an Apple product since 2007.)

They do have phone support, but they refused to unlock the account and just said she'll never be able to use primary email account with Apple's systems because of the frozen account.

So yes, any cloud provider can lock you out for arbitrary reasons. Just because they answer the phone doesn't mean the customer support agent can actually do anything about it.

At $1 / month having 50GB end-to-end encrypted storage and hide-my-email is reasonable in case your choice is better privacy over controlling your own mail domain.

Photos sync to iCloud is terrible slow though compared to Google Photos - syncing 100GB take days and 500GB takes forever. At least it end-to-end encrypted with Avanced Data Protection. But yeah if you multi-TB photo archive buying large storage options of iCloud make no sense simply because it's impossible to use.

I'd better use self-hosted Immich.

It has great features otherwise, I have like 100+ aliases with Hide My Email. You don't even need to use iCloud email with it.