YubiKey uses U2F and FIDO2/WebAuthn. The YubiKey also does a lot of other things, depending on which YubiKey you have... but if you want 2FA on random websites, those are the most likely protocols (used for GitHub and the like).
The basic U2F + FIDO2/WebAuthn is the least expensive model, around US$25. These days it works seamlessly on Chrome, Firefox, and Safari.
The basic U2F + FIDO2/WebAuthn is the least expensive model, around US$25. These days it works seamlessly on Chrome, Firefox, and Safari.