> Most clued-up places enable you to register a Yubikey as 2FA. So then it doesn't matter if you loose your OTP app and your backup codes because you've still got a Yubikey.

And what happens if you lose your Yubikey or it stops working? You're back to needing backup codes or an additional 2FA device

> And what happens if you lose your Yubikey or it stops working?

That's why you own N+1 Yubikeys ;p

Any place that offers Yubikey auth will enable you to register multiple Yubikeys against your account.

In all my time on the internet I have only ever seen one place that allows Yubikeys but restricts you to one key.