One of my yearly digital routines is to update my GPG key.
Part of this involves adding new ECC subkeys (ECDH and EdDSA).
These are the commands I used this time (so I don't have to look them up again next year).

% gpg --edit-key 401F1D483C69BF624364CC01E9A68DCFA3A54203

gpg> addkey
Select number 10 ECC signing
Select number 1 Curve 25519
Select a validity of 2y

gpg> addkey
Select number 12 ECC encryption
Select number 1 Curve 25519
Select a validity of 2y

gpg> save

After this the new subkeys are available and the updated public key can be exported and published.