Below code worked me - (able to login to public site without breaking sitecore login)
public class AzureAdB2CWsFedIdentityProvider : IdentityProvidersProcessor
private readonly string Idp = "idp";
protected override string IdentityProviderName => "AzureAdB2C";
private readonly string ...
Your dockerfile is missing a command to copy the development tools and entrypoint scripts from the tooling image. You can explore your identity container and verify that the tools directory doesn't exist.
Fix this adding the command COPY --from=tooling \tools\ \tools\ right after the SHELL command in your dockerfile build specs: