Mac users can use the native Micro.blog for Mac app. It’s a free download and supports most of the same features as the iOS version.
Download the latest version here. It requires macOS 10.12 Sierra.
When you first launch the app, it will prompt to sign in via your web browser. If you’re already signed in on the web, it will prompt to redirect back to the Mac version.
If you’re using a Micro.blog-hosted weblog, you can use File → New Post to start a new blog post. If you’re using WordPress or another server, first open the preferences window and enter your web site URL to set it up for posting within the app.