Man pages matching name gnutls_set_default_priority_append in section 3:

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