I'm willing to take the hit to subscriber numbers for not having that kind of thing on my own site.

From an SEO perspective, I think I might be beating Substack comfortably.

My blog has a different page for each item, plus it ties them together with tags.

The Substack email is a full week of content in one go. I don't think that's particularly SEO-optimal.

Again though, I'm willing to take the risk. So far I've not seen any obvious downsides to this model, and I've been dual publishing in this way for a few years now.