RSS.
I still don't "get" RSS feeds. I looked at one on Hubski once, and at a glance it looked like a normal Hubski page with less functionally and a "RSS" template. I don't have the faintest idea how to use RSS properly.
You can use a reader to aggregate a bunch of different RSS feeds together. It also keeps track of what you've read and not read. I use Tiny Tiny RSS, but there's also this, this, this, this, and more. I've been toying with the idea of making my own, too. I aggregate together a bunch of feeds from reddit, youtube, podcasts, webcomics, and blogs, and it keeps track of what I've read and not read (I'm actually super backlogged right now). Now that I've learned that hubski supports it, I'll probably add some feeds from here as well.
Oh! I actually was unaware that Hubski already supported RSS. RSS is the perfect solution for that, and there's already tools you can use to get email from RSS. That having been said, I'd support having an email notification if you decide that it's not too much more added complexity, but I probably wouldn't use it (I use an RSS reader anyway).
Yes, there might be better ways than an email as RSS almost creates that off-site option now. I kind of like the idea of being able to break your feed into tag-only, user-only, and domain-only content, as dashnhammit suggests.