Yes. Mutual TLS. But that involves certificates, potentially CAs, dealing with certificate expirations and other PKI formalities. Any user can generate an Ed255

Yes. Mutual TLS. But that involves certificates, potentially CAs, dealing with certificate expirations and other PKI formalities. Any user can generate an Ed25519 key pair, base64 encode the public part of the key and register that with websites. It's more informal than TLS certificates and totally user controlled. I do use TLS client certificates (with several APIs) but I don't consider them as password replacements (which is the goal of ed25519-login).