Recommended and mentioned products
A static-site generator written in Ruby
Jekyll is a simple, blog aware, static site generator.
Why the no longer maintained Jekyll Now vs. The current mainline Jekyll at https://jekyllrb.com/.
A minimal Markdown reading & writing app.
The combination of [Typora](https://typora.io/) for writing markdown + `mkdocs serve` or `hugo serve` is pretty neat. Set up a gitlab-ci.yml that builds and pushes the final site to your hosted destination.
A simple CMS for Jekyll and Hugo sites.
I'd suggest you give Forestry (https://forestry.io) a try. It's a great CMS for static sites (incl. Asset management) and it has a really nice preview system.
Manage your Notes from any Git Repo.
Disclaimer: App Author If your Hugo blog is stored in Git, you could try out GitJournal . It's a mobile based Markdown editor integrated with Git. Many people seem to use it for managing their Hugo/Jekyll blogs.  https://gitjournal.io  https://github.com/GitJournal.
Post articles online without an account at Telegram's anonymous publishing platform.
There is something already in place with the 'telegra.ph' site, which is connected with Telegram I believe: https://telegra.ph.
Kirby is a website for businesses to use to sort contacts and other information. The site is easy to use and features several details for businesses of all sizes.
I'm going to add my personal take on this issue since I'm currently running a blog that's markdown-ish powered. In my opinion the best solution is to find some sort of happy medium. Static site generators are excellent in terms of weight and speed but a lightweight file based CMS can be almost as fast while still providing the needed flexibility. My site currently runs on Kirby (https://getkirby.com) but I write...
A fast, simple & powerful blog framework, powered by Node.js
I ended up picking hexo, as the hexo admin plugin provides a nice localhost CMS/editor that supports image pasting, tag editing etc (could be hosted online too for remote/mobile access, but wouldn't be truly static/server-less at that point).  https://hexo.io/.
Zim is a graphical text editor used to maintain a collection of wiki pages. Each page can contain links to other pages, simple formatting and images.
Old school perhaps, but most everything here feels wildly overengineered for a static site. If the site is truly static, then there's no need for any server or client web languages at all. You need HTML (with perhaps some sort of generator), CSS, and e.g. rsync. I've been doing mine with http://zim-wiki.org for years.