Complain loudly on Twitter and hope your tweet goes viral.

Apple account recovery supports setting a recovery code or having a friend listed as a recovery contact.

Apple does not yet support Passkey for iCloud accounts login.

I use a yubikey. But AFAIK, Apple doesn't actually use passkeys for iCloud/Apple ID authentication.

Not yet, but Google wants them to become ubiquitous. So in that (far) future, backing your passkeys up in a cloud (that is also protected by passkeys) doesn't help

Call Tim, he'll vouch for you.