I have found by navigating to "Users > root > SSH authorized keys" and entering an ed25519 key the UI will present a message saying "Syntax of the key is incorrect". I dug into the frontend and found the javascript function that is being used to check the validity of keys entered into this field and it looks like it only allows rsa and ecdsa keys. ed25519 is somewhat new, but is supported in the version of openssh (8.8) included in unRAID 6.10.3. SSH key pairs using security keys (ex: yubi