[dhdhhdd]

I so wish u2f/yubikey was supported on all websites :-(

[Zetobal]

I use the yubikey authenticator app for the ones that don't. The secrets are saved on the key and you can password protect it... and as with all keys back it up to your spare.

[latchkey]

When you're traveling to Costa Rica, where do you keep your spare? Do you stay locked out until you get home? What if you're a nomad and you don't have a 'home'?

[Zetobal]

One of my spares is usually with my spouse (it's still password protect) and if both get lost I kinda deserve to be logged out until I get home.