Looking for logging into the U2f Php site and are not getting the correct working link for it? In such a case, you can use the links given here by searching your desired login page in the search box. If the page is present on our website then you will get all the links related to the U2f Php site. After that you can login as usual with your login credentials.
https://github.com/Yubico/php-u2flib-server
https://github.com/Firehed/u2f-php
https://developers.yubico.com/php-yubico/
https://stackoverflow.com/questions/26637660/how-do-i-use-fido-u2f-to-allow-users-to-authenticate-with-my-website
https://www.sebastian-eggersberger.de/blog/wordpress-mit-fido-u2f-absichern-so-gehts/
https://packagist.org/packages/samyoul/u2f-php-server
https://de.wikipedia.org/wiki/U2F
http://docs.phpmyadmin.net/es/latest/two_factor.html
https://de.slideshare.net/FIDOAlliance/u2f-tutorial-authentication-tokens-for-enterprise-and-consumers
https://security.stackexchange.com/questions/71316/how-secure-are-the-fido-u2f-tokens
https://www.wired.com/story/how-to-use-a-yubikey/
https://libraries.io/search?keywords=u2f&languages=PHP
https://wiki.archlinux.org/index.php/YubiKey