Migrating users without username/password

I’m considering Auth0 for a project with thousands of already active users. I was trying to understand what’s available for the user migrations such as here: https://auth0.com/learn/migrate-user-database-auth0/

However, my users do not currently use a username and password. 100% of my authentication today is through SSO (either social, or enterprise saml). Is it at all possible for the automated on-the-fly migration to work without a username and password combo? I’m not finding many examples.

I am also keen to find out about this as a section of our users were created using Social and have no password.

I’m stuck here too… we’ve unfortunately got users who’ve create accounts with email/password and then also signed up with Facebook instead of linking their accounts… so in our case the email isn’t a unique lookup.

Our plan is to use rules to check out current store via username / password or provider type / provider key and return the User Id…

Basically the whole exercise to link the IDs of existing users to their Auth0 profiles so when they hit the api we can tell who they are based on established IDs