No, you can't. You need to login into every website and replace passkey with new one in website-specific way.

You can use passkeys cross platform already, eg with 1Password or even KeePass XC.

But I do agree with the point that Passkeys make it really easy to get locked in unless you’re careful.

"We do not support competitors' products."

No, you add a new passkey from Android and then remove the passkey from iPhone.

1. Login with the passkey from your iPhone.

2. In your account, add a new passkey from your new Android. Now both passkeys are active.

3. Login with your new Android passkey.

4. In your account, deactivate the passkey that is stored on your iPhone.

Passkeys aren’t passwords. You can have more than one active at the same time. So instead of moving a single passkey around, you add or remove them to change devices or service providers.