Joplin
Open source note taking and to-do app with synchronization
... with cloud services, notebooks, tags and other metadata can easily be moved, inspected or backed up as plain text files. Supported cloud services include Nextcloud, OneDrive, Dropbox and WebDAV.
Joplin is available for Windows, Linux, macOS, iOS and Android, with three types: desktop, mobile and terminal. All of them have similar user interfaces and can be synchronized with each other.