Man pages matching name curlopt_low_speed_limit in section 3:

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