If you're using markdown and js, in what sense are you blogging in raw HTML? Not to doubt but it feels like a qualified version of the underlying state of affairs.
I blog (for work) on WordPress and hate it. I could imagine using org mode or markdown, pandoc to emit HTML with some tuning and a simple script to publish via sftp.
If I turn off Javascript, your blog breaks in ways that shouldn't be possible if it really was HTML (specifically, links and images disappear[0]). You're not blogging in raw HTML, but markdown. Your homepage is the most 'raw HTML' page I can find on your blog, because it uses real HTML elements to display things, and doesn't even use JS or CSS.
It's a GitHub Action that regularly scrapes your page and checks for new entries, turning it into an RSS feed. Set up a redirect yourblog.com/feed -> you.github.io/feeds/feed.xml, then you're golden.
The moment you add an RSS script you cease to use raw HTML and start to use your own bespoke site generator.
On the plus side, a personal project only changes when you intend for it to, so you don't need to worry about breakage. (Unless your scripting language breaks.)
I can write a script to generate that from the list of article but I'm not sure if there's better way.