We don't have a formal RSS feed on this platform. I don't recall it on our last one either. But you can click on the 'Follow' button listed at the top of the Forum/Topic that you're interested in to follow any topic you want. This will copy everything into your My Community tab. Then when you log in to the Communities, you can go to your My Community tab and see the content there.
We're also working on enabling the 'Follow' function for individual threads, that's an item coming soon. Just @mention me if you have more questions. Thanks,