I just finished and released my MVP on https://norde.io
The landing page isn't much to look at at the moment and Norde Source is far from complete and full of bugs but it does do the bare minimum of being an icon manager and it's a great feeling to have something to show and distribute.
The main thing setting it apart from the competition at the moment is that it's file-based so any work you do to organize your categories and files will be mirrored in your icon folder. So if you ever decide to stop using Norde Source or want to access the files through something else, your files and folders will be neatly organized just like you had them in the app.
Besides squashing bugs and adding more basic features, like ability drag and drop to other programs, managing tags, I'm planning on adding multi-color icon support. That will allow Norde Source to detect multiple colors in icon sets and let you change each color for the entire set and see it reflected in the entire set.
The end-goal is for Norde Source to be more than just an icon manager. Also upcoming is project related asset management. That would include managing project color schemes to easily apply the projects colors to other assets like your icon sets. As well as managing things like logos, fonts and even stock images.