misusing USB keycards?

The consensus on Debian seemed to be Yubikey is in general very neat. It's amazingly robust, it's got all the features you want, and if they begged and pleaded enough they could probably get it at the right price. It's a consensus I agree with, as I use the things in my day job.

The fly in the ointment is its proprietary. Ergo some assume it's probably backdoor'ed. I'd be acting on the assumption too, even though I think on the balance of probabilities it's not. Add closed + proprietary and Debian don't mix well, and it doesn't look like Yubikey would fly with Debian.