2FA/U2F - Two Factor Authentication

1) 2FA with Google Authenticator

2) FIDO2, U2F dongle support

Yubikey
https://www.yubico.com/
https://www.yubico.com/why-yubico/how-the-yubikey-works/

Technical documentation for developers:
https://www.yubico.com/why-yubico/for-developers/
Self-verified integration or Yubico-verified integration:
https://www.yubico.com/works-with-yubikey/

After implementation, it would be nice to add to the directory:
https://www.yubico.com/pl/works-with-yubikey/catalog/

By the way, it is also an advertisement, because the promoted U2F solution in the catalog.