Notesnook (https://notesnook.com/ https://notesnook.com/) - it's open source, has its own importer making it super easy to migrate, is fully cross platform, and

Notesnook (https://notesnook.com/ https://notesnook.com/) - it's open source, has its own importer making it super easy to migrate, is fully cross platform, and doesn't force you to learn-and-relearn anything. It's note taking - just perfect-er.