UpNote - A beautiful and clean cross-platform app for notes organizer

Turtl - The secure, collaborative notebook

Notesnook - Notesnook is a simple and private note taking app that keeps your notes organized and synced on your phone, tablet and computer.

Omni Notes - Note taking open-source application aimed to have both a simple interface but keeping smart behavior

Note Board - Productivity app. Save information like a sticky notes.

Cryptee - Cryptee is a safety and privacy focused, encrypted and cross-platform personal data storage service. You can write personal documents, notes, journals, store photos and all sorts of other files.