Turn a $5 Raspberry Pi RP2350 board into an open-source hardware passkey: WebAuthn/FIDO2 logins, ssh & git signing, OpenPGP, PIV, TOTP. Rust firmware, no_std.
Server-side Web Authentication library for Java https://www.w3.org/TR/webauthn/#rp-operations
FIDO Passkey for Raspberry Pico and ESP32
FIDO-U2F / FIDO2 / Webauthn Framework