Man pages matching name curlopt_ignore_content_length in section 3:

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