Thank you for the question! Hope you're doing well.
Presently, Teachable only supports incoming SSO. It means that you can use different methods available on their website to authenticate your Teachable access using Single Sign On. They don’t offer any outgoing SSO hence the SSO with teachable is not an option yet. The workaround is to use a middle SSO (like WordPress OAuth) and authenticate users on both platforms using that SSO.
Hope this answers your question!