[...nextauth].js

import NextAuth from "next-auth";
import AzureADProvider from "next-auth/providers/azure-ad";

// This really is the default config, the issue only occuries in combination 
// with the Azure AD config and I can not give you my secrets.
// Please keep reading the issue, thank you :)

export default NextAuth({
  providers: [
    AzureADProvider({
      clientId: process.env.AZURE_AD_CLIENT_ID,
      clientSecret: process.env.AZURE_AD_CLIENT_SECRET,
      tenantId: process.env.AZURE_AD_TENANT_ID,
    }),
  ]
});