If you want users to log in to your Joomla site using their Twitch credentials, you can do it using our Joomla Twitch OAuth plugin. Once you configure the Twitch with the Joomla OAuth plugin, you can allow Twitch users to SSO into your Joomla site using Twitch.
Similarly, you can map your Joomla roles based on your Twitch attributes/groups. To know more about other features we provide in the Joomla OAuth plugin, you can download by click here.