Joplin
From What is 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, can be copied, tagged and modified either from the applications directly or from your own text editor. The notes are in Markdown format.
Joplin is "offline first", which means you always have all your data on your phone or computer. This ensures that your notes are always accessible, whether you have an internet connection or not.
The notes can be securely synchronised using end-to-end encryption with various cloud services including Nextcloud, Dropbox, OneDrive and Joplin Cloud.
Full text search is available on all platforms to quickly find the information you need. The app can be customised using plugins and themes, and you can also easily create your own.
The application is available for Windows, Linux, macOS, Android and iOS. A Web Clipper, to save web pages and screenshots from your browser, is also available for Firefox and Chrome.
Installation
Install joplinAUR for the Joplin Terminal application.
Install joplin-desktopAUR for the Joplin Desktop application.
Synchronization
See the official documentation on Synchronization for instructions on how to sync notes across devices using either cloud-based or offline sync.
Plugins
The desktop application can be extended with plugins. Plugins are not available in the Terminal application.
See the official documentation on plugins for information on installing plugins. The desktop application downloads plugins into ~/.config/joplin-desktop/plugins.
Tips and tricks
Importing Notes from Other Applications
See the official documentation on Importing and Exporting for instructions on importing notes from Evernote, OneDrive, and other note-taking applications.