Hi @Mike , yes, you can use Azure AD B2C as an identity provider (IDP) in your Azure AD B2B collaboration.
To do this, you need to configure Azure AD B2C as an external IDP in your Azure AD tenant. Once you have done this, you can invite external users to collaborate with your organization by sending them an invitation link. When the external user clicks on the invitation link, they will be redirected to the Azure AD B2C sign-in page where they can sign in with their B2C credentials.
After the user has signed in, they will be redirected back to your application and will be granted access based on the permissions that you have configured for them.
Keep in mind that you will need to configure your application to accept tokens from Azure AD B2C as an IDP. You will also need to ensure that the user accounts in Azure AD B2C are properly configured to grant the appropriate permissions to access your application.
Please let me know if you have any questions and I can help you further.
If this answer helps you please mark "Accept Answer" so other users can reference it.
Thank you,
James