Joplin
joplinapp.org
Open-source note-taking and to-do app with end-to-end encryption — a free, cross-platform alternative to Evernote.
Why it is useful
Joplin supports Markdown notes, notebooks, tags, and to-dos across desktop, mobile, and terminal clients, with optional end-to-end encrypted sync to your own storage (Nextcloud, S3, WebDAV, or Joplin Cloud). It gives Evernote-style organization without a subscription or Evernote's shrinking free-tier limits.