It should be LightPasswordCredential. What is the instance then?
Once you reach the permission page, it is working :)
I am writing a new authenticator for light-portal user management integration. It will take another two or three days.
@went-li While I am writing a tutorial about customized authenticator in light-oauth2, I thought it might help you to check out the code first. Take a look at the implementation at networknt/light-oauth2#236