[m0dest]

This is the million dollar question that Apple hasn't answered. What happens to these forwarding addressses if you cancel iCloud+?

The result is bad either way. It's either A or B. (A) Canceling iCloud+ doesn't remove existing Hide My Email addresses - which makes it possible to abuse by creating tons of extra addresses before canceling. Or: (B) Canceling iCloud+ deletes all of your Hide My Email addresses, locking you out of dozens of services (e.g. anything that sends an email as a MFA).

I suspect that it is actually (A). Someone just needs to test this and report out.