Comment by cnst

They're not the same, they're completely different:

> Additionally, all the post-quantum algorithms implemented by OpenSSH are "hybrids" that combine a post-quantum algorithm with a classical algorithm. For example mlkem768x25519-sha256 combines ML-KEM, a post-quantum key agreement scheme, with ECDH/x25519, a classical key agreement algorithm that was formerly OpenSSH's preferred default. This ensures that the combined, hybrid algorithm is no worse than the previous best classical algorithm, even if the post-quantum algorithm turns out to be completely broken by future cryptanalysis.

The 256 one is actually newer than the 512 one, too:

> OpenSSH versions 9.0 and greater support sntrup761x25519-sha512 and versions 9.9 and greater support mlkem768x25519-sha256.