You can self-service purchase a YubiKey through our centralized ordering portal. YubiKeys cannot be purchased and expensed separately unless pre-approved by IT for countries that we do not support shipping to.
Your YubiKey is used for two factor authentication (2FA) using the WebAuthn protocol. Several other protocols are supported by YubiKeys (OTP, U2F, etc.) however they are not used at GitLab. This guide provides a getting started to use your YubiKey for WebAuthn.