I don’t know when Netlify published that article, but there have been changes to how .Pages works in recent versions of Hugo. You probably want .Site.RegularPages.
If that is not enough to fix your issue, please read Requesting Help to see what information we need to be able to help.
I am able to build (at least the homepage). You are missing at least a _default/list.html and _default/single.html layout files, so Hugo has no way of knowing how to build the rest of your pages.
I suggest not just randomly trying themes; instead use the tags. Looking at the themes tagged starter for example and I see a Blank theme, as well as a couple other minimal-looking themes.
If by minimum, you mean the least amount of files, just the two _default files I mention above will get Hugo to generate your site.
hugo new site testsite
cd testsite
hugo new theme themetest
echo 'theme = "themetest"' >> config.toml
echo '{{ .Content }}' > themes/themetest/layouts/index.html
echo test > content/_index.md
hugo serve
test does show, but it kindof falls short of a “hello world” for a Website. I’d expect at the minimum:
HTML
Concept of posts
RSS feed
I wish I could filter out all the crazy (webpack) JS/sCSS pipelines from https://themes.gohugo.io/tags/starter/ and also see the latest ones in light of the scary breaking " Site.RegularPages" change.