You can use facebook custom audience feature by providing a sha256 hashed value and use those to create custom audience using facebook-ads-api.
here are some relevant links to get you started :
https://developers.facebook.com/docs/marketing-api/audiences-api/
and here are some notes if link clicking is not your thing:
Hashing and Normalization for Multi-Key
You must hash your data as SHA256; we don't support other hashing mechanisms. This is required for all data except External Identifiers, App User IDs and Page Scoped User IDs. Before hashing, normalize your data.
Email addresses - Use key EMAIL. Trimming leading and trailing whitespace and convert all characters to lowercase.
Provide SHA256 values for normalized keys and HEX representations of this value, using lowercase for A through F. The hash function in PHP converts normalized email and phone number:
example : hash("sha256", "mary@example.com")
f1904cf1a9d73a55fa5de0ac823c4403ded71afd4c3248d00bdcd0866552bb79