A Hardware Security Key is a small physical device used for additional security next to your password and is considered to be one of the most secure ways of two-factor authentication (2FA). Most Hardware Security Keys are very simple and you only need to touch or tap a button while it is plugged into the USB port of your device.
At this moment only sign-in 2FA can be secured with both FIDO2 and Yubico OTP protocols. Sign-in 2FA and the Master Key support Hardware Security Keys that use the FIDO2 protocol. Funding 2FA only supports the Yubico OTP protocol.