PBKDF2 is a key derivation function recommended by IETF in RFC 8018 as part of the PKCS series, even though newer password hashing functions such as Argon2id or Argon2i are designed to address weaknesses of PBKDF2. It could be a preferred password hash algorithm if storing passwords in a FIPS compliant way is necessary. Usually, selecting Argon2id or Argon2i if available as hash algorithm is ideal. PBKDF2 is not available on this system. This is very uncommon. If Argon2id, Argon2i and bcrypt are also not available, you should reach out to your hoster to fix this as soon as possible.