Other devices attached to the existing II include a Yubikey and an iPhone.
When attempting to add the MacBook from the iPhone, clicking “Add New Device” prompts the question, “Do you want to allow ‘identity.ic0.app’ to use Face ID?” And when I click “Continue,” the activity indicator spins without resolving.
When attempting to add the MacBook using my other computer with the Yubikey, clicking “Add New Device” prompts me to enter my security key and touch it, after doing which the prompt answers that I have already added the given Yubikey. Presumably this means I can only add another token using this workflow.
When attempting to add the MacBook using the MacBook itself, by clicking “Already have an anchor but using a new device?,” I am prompted to “insert [my] security key and touch it” - but this MacBook doesn’t have a port to enter the Yubikey.
So how does one add a touch-ID-enabled MacBook?