Official web site: https://www.yubico.com/products/, The YubiKey is a hardware authentication device manufactured by Yubico to protect access to computers, networks, and online services that supports one-time passwords, public-key cryptography, and authentication, and the Universal 2nd Factor and FIDO2 protocols developed by the FIDO Alliance.

https://github.com/drduh/YubiKey-Guide  - Guide to using YubiKey for GPG and SSH
https://github.com/herlo/ssh-gpg-smartcard-config  - Configuration to use gpg smartcards for ssh authentication
https://trmm.net/Yubikey/

https://github.com/obelisk/rustica  - About An SSHCA that uses a standard Yubikey to issue new host and user certificates.
https://github.com/obelisk/sshcerts  - A crate for reading, parsing, verifying, and generating OpenSSH certificates and keys

https://github.com/keepassxreboot/keepassxc  - KeePassXC is a cross-platform community-driven port of the Windows application “Keepass Password Safe”
https://github.com/pp3345/ykDroid  - YubiKey challenge-response USB and NFC driver for Android
https://github.com/PhilippC/keepass2android  - Password manager app for Android
https://keepass.info/download.html
https://github.com/noliran/ykpass  - Use your YubiKey as a consistent password generator