Whatever is 100% free, non-commercial and independent project. It is not supported by Evernote© corporation or any other commercial organization.
Since Whatever is on active development stage, feel free to contribute and open issues on GitHub.
Whatever is based on web-technologies and Electron framework.
Whereas Evernote Corporation still doesn't support Linux platform, there is a 100% freedom for third-party developers to piece it out, as it is mentioned at the official Evernote support page.
Whatever provides native installers for the most popular Linux distributions. Also it can be built from the source code.