Sorry for taking so long to reply.
So, thing is I fixed the code on the openid passport provider manually changing a couple of lines.
I've started looking around to see if someone did the same as I did and, someone indeed has here: https://github.com/elendirx/ignum-passport-openid
They even added more features and fixed more things
Now, thing is that the passport-steam should use that openid passport instead of the original one, as that one doesn't support the returnURL parameter and else (which is required for the CSRF token). So, i'm going to see if I can find a package that supports the new OpenID passport and if so, i'm going to make a new plugin for the Steam login of NodeBB and publish it on NPM.