Man pages matching name d2i_pkcs8privatekey_bio in section 3ssl:

d2i_PKCS8PrivateKey_bio.3ssl.en	debian 10 / libssl-doc
d2i_PKCS8PrivateKey_bio.3ssl.en	debian 11 / libssl-doc
d2i_PKCS8PrivateKey_bio.3ssl.en	debian 12 / libssl-doc