Man pages matching name gnutls_encode_gost_rs_value in section 3:

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