The https://freepg.org/ project maintains patches against #GnuPG with the goal of closer adherence to the IETF #OpenPGP spec.
One currently open question is if/how draft-ietf-openpgp-pqc support could be realistically added to #FreePG
I've started https://codeberg.org/freepg/freepg-draft-ietf-openpgp-pqc first of all as a notes-to-self repo for a (presumably very slow and long-term) side quest to explore this problem.
Specifically, the goal would be adding support for v4 ML-KEM-768+X25519 subkeys.
https://www.ietf.org/archive/id/draft-ietf-openpgp-pqc-17.html#ecc-mlkem
