Man pages matching name curlopt_gssapi_delegation in section 3:

CURLOPT_GSSAPI_DELEGATION.3.en	debian 10 / libcurl4-doc
CURLOPT_GSSAPI_DELEGATION.3.en	debian 11 / libcurl4-doc
CURLOPT_GSSAPI_DELEGATION.3.en	debian 12 / libcurl4-doc