Signal is upgrading all conversations to a combination of X25519 and CRYSTALS-Kyber. Probably the first large-scale deployment of Kyber. https://signal.org/blog/pqxdh/
Discussion
do cryptographers think of kyber and others as a good foundation for ‘post-quantum’ (ie when it actually works) cryptography, or are they just viewed as placeholder hacks.
sphincs looks good, kyber not quite. I think Signal's decision is proper and other should follow, because it's hybrid. In the end, everything is a placeholder, and the only question is: "for how long?".