Your notes already are the backup
Many notes apps promise an export. Whether it's any good usually shows on the day you need it: links turn into titles, formulas into fixed values, images go missing.
tagwerk has no export, because it doesn't need one. Every day is a Markdown file in a folder you pick. The folder is the backup. Any editor opens it, and grep, diff and git work with it.
What a single file can't do is remember yesterday. That's why every day in tagwerk has a history. The app keeps up to 20 earlier states of a day, for half a year. For each one you see what restoring it would change, and the current state is kept as well. The history is part of the free version.
The history lives on each device. It's meant for the moment you realise you didn't want to delete that. For years, and for the day a device gets lost, keep the folder somewhere with versions of its own: Nextcloud, OneDrive, a Git repository or any other service that keeps versions. Because the notes are plain text files, any of them works.
tagwerk is free on Android and Windows. Linux is on its way.
Get it from the Microsoft Store
Questions or ideas? Write to me, I read everything.
Tom