Flat Notes is described as 'The notes app with Google Keep design for Windows 10' and is an app in the Office & Productivity category. There are more than 50 alternatives to Flat Notes for a variety of platforms, including Windows, Android, iPhone, Online / Web-based and Mac. The best alternative is Joplin, which is both free and Open Source. Other great apps like Flat Notes are Standard Notes (Freemium, Open Source), Google Keep (Free), Microsoft OneNote (Freemium) and Evernote (Freemium).
Joplin is a free, open source note taking and to-do application, which can handle a large number of notes organised into notebooks. The notes are searchable, can be copied, tagged and modified either from the applications directly or from your own text editor.
Colorful & powerful sticky notes app for Windows & Phones. Set reminder alarms, attach them to any website or document, organize them using folders/tags, sync sticky notes between devices & send notes across LAN or to any contact across the globe.