Man pages matching name gnutls_prf_rfc5705 in section 3:

gnutls_prf_rfc5705.3.en	debian 10 / gnutls-doc
gnutls_prf_rfc5705.3.en	debian 11 / gnutls-doc
gnutls_prf_rfc5705.3.en	debian 12 / gnutls-doc