At the moment I seem to be able to checked the ranked box when creating a rengo game and it disappears when I uncheck the ranked filter at the bottom of the play page.
Whether that means anything I don’t know, I can’t imagine whether it will try and do some weird rating calculation at the end or not even let the game start 
That is
I think I possibly missed @_Sofiam ‘s open challenge on beta, I probably went offline at that point.