Replying to a post on mastodon.social
@Edent RFC9421 only lists a handful of possible algorithms. IIRC if your key is ed25519 only one of them applies, similarly if the key is ecdsa. I think there are two possibilities for RSA keys, but we only support one for legacy reasons and do not plan to encourage future use of RSA so will likely never implement the other. So in practice looking at the key type should be sufficient to determine the algorithm used.