Haroopad is described as 'Markdown enabled document processor for creating web-friendly documents. You can author various formats of documents such as blog article, slide, presentation, report, and e-mail as if experts did' and is a popular Text Editor in the news & books category. There are more than 100 alternatives to Haroopad for a variety of platforms, including Mac, Windows, Linux, Web-based and Flathub apps. The best Haroopad alternative is Sublime Text, which is free. Other great apps like Haroopad are Vim, Zettlr, Typora and Neovim.
Very similar in layout and usage, with the two-pane layout with the markdown on the left, and the preview happening in real-time on the right.