Joplin - 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, tagged and modified either from the applications directly or from your own text editor.
Buno - Simple Note Taking - Simple, minimal & easy note-taking
Boostnote - Boostnote is an open-source note-taking app.
Text Case - Format any raw text on iOS and more 📝
Standard Notes - A safe place for your notes, thoughts, and life's work
Chars - Unicode Symbols Keyboard for iOS