You can use a software passkey and still get 99% of the benefit. For the other 1%, you can't have it both ways, where a hardware key is both required and not required to sign in.
Maybe there can be better UX around signing up, ie "give me your public keys so I can set them up in your account", but then you lose a lot of the privacy, because the public keys aren't different per site any more (and operators can then tell the same person has an account on multiple sites).
Maybe there can be better UX around signing up, ie "give me your public keys so I can set them up in your account", but then you lose a lot of the privacy, because the public keys aren't different per site any more (and operators can then tell the same person has an account on multiple sites).