Apostrophe is described as 'simple GNU/Linux Markdown editor built with the GTK+ framework' and is an app in the Development category. There are more than 10 alternatives to Apostrophe for a variety of platforms, including Linux, Windows, Mac, Android and iPhone. The best alternative is Typora, which is free. Other great apps like Apostrophe are Mark Text (Free, Open Source), ghostwriter (Free, Open Source), ReText (Free, Open Source) and Rentry.co (Free).
No excuses. No distractions. Just write. ghostwriter is a feature-rich text editor using Markdown syntax which makes it suitable for note-taking, document redaction, simple HTML website creation and much more.
ReText is a simple text editor for Markdown and reStructuredText documents with syntax highlighting and optional live preview. It is written in Python using Qt libraries, able to run on any platforms (Linux and BSD are officially supported).
Buho is a note-taking app. Buho will let you take quick notes, save links, create books and pages for taking classes notes. It is free and multi-platform, and open source under the LGPL v3 License. Index is made with Mauikit.