I've been using the RSS link at the top of the page after finding what I'm looking for in the Communites and clicking the title there. For example, after clicking the link for the top Community listed in All, it takes me to https://lemmy.sdf.org/c/asklemmy@lemmy.ml and there's an RSS link next to the filters.
However, I've since figured out I prefer using just 1 RSS feed and that's my Subscribed filter https://lemmy.sdf.org/?dataType=Post&listingType=Subscribed&page=1&sort=Hot. I was very delighted to find that it works the way I expected without have to do any kind of authenticated RSS url. When I follow a new community they just start showing in my main feed. Now I just have to pick between Active, Hot or New. Using Active currently.