Based on Local User starter pack and UserInfo custom policy docs.
Use standard OIDC request with this policy. Then:
GET https://yourtenant.b2clogin.com/yourtenant.onmicrosoft.com/policy-name/openid/v2.0/userinfo Authorization Bearer <id_token>
Use IefPolicies module with the following command
Add-IefPoliciesSample UserInfo -owner mrochon -repo b2csamples