While testing FIDO2 on iOS 14.0 18A5319i with a YubiKey 5Ci, the key LED blinks but Safari does not recognize the activation gesture. The key prompt dialog can only be cancelled. This same key works on the Brave browser on the same phone/OS. I was also able to get Face ID to work for FIDO2 (awesome!) on Safari on the same phone/OS. Please let me know what information I can provide to help debug this.
My 5Ci works for me on webauthn.io. Are you using a Yubico internal test device or a production one?
<rdar://problem/66205835>
It was a shrink-wrapped production device.
This may be an issue with the Yubikey being used by the system as an OTP device (fake keyboard) rather than a FIDO2 device. The easiest way to tell if the device is in an active FIDO mode is if the LED is flashing. If you want to experiment with disabling OTP functionality, you can enable and disable functions of the key using the command-line tool at https://www.yubico.com/products/services-software/download/yubikey-manager/ with a desktop or laptop computer.
Thank you for the suggestion! I disabled all interfaces (including OTP) except for FIDO2 but I still have this issue. Why would it work for Brave but not Safari? Brave doesn't have any trouble detecting that I've activated the key.
*** This bug has been marked as a duplicate of bug 215836 ***