Man pages matching name gnutls_openpgp_privkey_sign_hash in section 3:

gnutls_openpgp_privkey_sign_hash.3.en	debian 10 / gnutls-doc
gnutls_openpgp_privkey_sign_hash.3.en	debian 11 / gnutls-doc
gnutls_openpgp_privkey_sign_hash.3.en	debian 12 / gnutls-doc