I found a fix. It was an error in nodebb. When I did ./nodebb setup I made a typo in the port.. oops .-.
Anyway its all good now.
I follow the steps in readme of this plugin. Modified code and activate it without error message. But the login page is as before without any sso link. So how can I kick off the sso login process? Thanks a lot.
It seems others can get the "Alternative Login" button in login page, but I can't... I just clone the repo, add code, copy the folder into node_modules, then activate it in ACP. Did I miss something?