Underverse is usable, but there is no stable binary release.
Use at your own risk!

• Portable
• Markdown editor and note-taking tool in one application
• Image/attachment/linking support
• Text search in notes

Explicitly not supported is:

• Synchronizing notes between different devices!
  Use your favorite clould drive (e.g. GoogleDrive, OneDrive, DropBox) or version control system (e.g. SVN, GIT) for that!

Please use git to clone the most recent development version:

git clone --recursive https://github.com/marc-sturm/Underverse.git

Then, open the src/Underverse.pro file in QtCreator and build the application.
After a successfull build, the binary can be found in the bin folder.