@lauratommasina To my knowledge, this will depend on which member gating service you use. I’ve only ever used Memberstack (which does not offer SSO with Discourse), however a quick google search suggests that Memberful may offer this functionality (unsure how compatible it is with Webflow, though).
An alternative would be a solution I’ve used before - combining Memberstack (which works nicely with Webflow) and Circle.so - SSO works nicely between these services and you can even gate Spaces within Circle according to membership tier by using an automation service such as Integromat to bind it all together.
Circle is pricier though, so that’s the trade off I guess!