Man pages matching name pcre2_substring_length_byname in section 3:

pcre2_substring_length_byname.3.en	debian 10 / libpcre2-dev
pcre2_substring_length_byname.3.en	debian 11 / libpcre2-dev
pcre2_substring_length_byname.3.en	debian 12 / libpcre2-dev