Auth: import users with MD5 passwords

[David]

I am after importing identities into Firebase including password hashes.

The legacy password hash algo is a salted MD5 with more than 8192 rounds, which seems to be common in some Drupal or Typo3 instances.

However Firebase supports only 8192 rounds for MD5: https://firebase.google.com/docs/auth/admin/import-users?hl=en#import_users_with_md5_sha_and_pbkdf_hashed_passwords

What are my options given I don't want to force users to change their password after the migration? In other words the old password should be imported along with user profile data and users should be able to login with the same password after the migration to Firebase.

Thanks!