Hmm, in your https://github.com/followbl/webpack5-next-auth/blob/main/pages/api/auth/%5B...nextauth%5D.ts I cannot see that you actually configured a database.

The Email Provider can be used with both JSON Web Tokens and database sessions, but you must configure a database to use it. It is not possible to enable email sign-in without using a database.

See: https://next-auth.js.org/providers/email

This is because the generated token must be saved somewhere (in a database).

Another thought is that https://github.com/christkv/require_optional causes problems with Webpack 5. We really should be getting rid of it in my opinion. It hasn't been maintained for 3 years now, and it is openly just a hack for something that should be built-in. Looks like it finally is:
npm: https://docs.npmjs.com/cli/v7/configuring-npm/package-json#peerdependenciesmeta
yarn: https://yarnpkg.com/configuration/manifest#peerDependenciesMeta

Had an issue mentioning it, but nothing happened since then: #1012

I am no expert on the topic, and I don't know how breaking this change would be, or if it is even a solution for your problem you are facing. I also haven't used Webpack 5 yet.

cc @iaincollins might have some other ideas.

@balazsorban44 I can update the example to be valid, but to be clear this happens for any configuration though...it's unrelated to email provider vs any other provider.

@balazsorban44 went ahead and made this a valid example for you, error still shows up. https://github.com/followbl/webpack5-next-auth/blob/main/pages/api/auth/%5B...nextauth%5D.ts

Lmk, if there's a specific ask you'd like me to look in to around the peerDependencies configuration you mention above.

could you link me to where it says it's not recommended? #2048 is an issue about exactly that usecase!

Update: I think I found it vercel/next.js#20487 (comment)

@balazsorban44 yup. That's the one - my apologies I didn't include.

Learn something new everyday - excited to be on webpack5 now.