Yubikey is one of the most simple and safe ways to set up 2FA. Further information can be found at:
If you already have an XGo account, you can use it to log into the app. However, if you use a Yubikey as the only means of two-factor authentication, you'll need to add a 2FA app as another method of two-factor authentication on our website before you can sign in to our app. Then just use the one-time code to sign in to your account.
For more information on 2FA, just take a look here.