Can I use a yubikey U2F as a second-factor for iCloud sign-in on Mac OS X?

No. The following has information about Apple two-factor: Two-factor authentication for Apple ID - Apple Support

Also, for a complete list of YubiKey supported services, see: https://www.yubico.com/works-with-yubikey/catalog/

No. I would be very surprised if they ever did but I have no information about unannounced plans.

John Clements wrote:

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(To be sure, this is different from my original question; that is, whether I could use such a token for 2FA with iCloud.)

Thanks!

Correct. Apples two-factor authentication is designed to protect access to your Apple ID only and not to protect access to any devices.

On 17 Oct. 2018 2:39 am, "Apple Support Communities" <