I know that providing template with authentication was one of the issues someone wanted to incorporate, but I couldn't find this implementation in their github repo. Do you have any helpful links for this? I've been trying to get Auth0 to work with MERN.
I dont do MERN, but on my last React project I used Amazon Cognito user pool service. It has permanent free tier for 50.000 (active!) users per month and I can tell you I'm not writing any more custom code for authentication, login/register/forgot password/email confirmation, etc. Haven't used it, but you can also do federated Identites easily.