@omega I actually meant "according to the docs".
I am sorry for my crappy English as I am not a native speaker.
I wrote a tutorial about setting up single sign-on for NodeBB.
Full disclosure, I wrote it using my employers OAuth server (FusionAuth) as the user identity provider.
But the plugin and steps should work with any OAuth server. The plugin is here: https://github.com/FusionAuth/nodebb-plugin-fusionauth-oidc