Greenbush
No, GrapheneOS is based on Android (AOSP) which limits authentication methods to only knowledge factors (PIN/Password/Pattern) and Biometrics for quick unlock after first unlock (AFU).
Android currently doesn't support hardware keys like FIDO2, U2F or OTP for unlocking the device.
Yubikey can emulate a keyboard so it can auto-type a static PIN or Password, but this is very insecure. OnlyKey also auto-types passwords and is protected by an onboard 6-button PIN, but do you really want to set a really long, random password for your phone, and then need a hardware token with a USB-C adapter? It'll take 20 seconds to unlock the phone. The only benefit to security is if you keep the phone and they key separate.