I have main Q&A site and i have done many Q&A sites ...user wants to login through my main site or sub domain site..
It is possible ...
My site http://asktoweb.com/ is main website.i have many sub sites are like http://boardgames.asktoweb.com/,http://anime.asktoweb.com/ more like..
Check this may any of this helps you.
Welcome to the Q&A site for Question2Answer.
If you have a question about Q2A, please ask in English.
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July 15, 2020: Q2A 1.8.5 released!