I don't like subscription popups - see recent John Gruber rants on the subject: https://daringfireball.net/2026/05/what_is_a_dickover
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.
Thank you! My coauthor Brad and I were subscribing to Ghost just yesterday ; we're going to adopt your model.