What's a simple OneDrive-like backup option for Linux?

First, decide whether you need syncing, backups, or both. A sync folder keeps files available across devices, but an accidental deletion can sync too. Some services have file recovery or version history, though the details vary.

For an actual backup, look at Déjà Dup. It can run scheduled backups and restore older files. An external drive is a straightforward destination. Check that it is connected when backups are due, and try restoring a file so you know the backup works.

You don't necessarily have to give up OneDrive. There is a third-party Linux client, though it takes more configuration than the Windows integration. If keeping your existing storage matters more than having a polished setup, that's worth a look.

For a hosted sync service, check out Filen or Dropbox. Both have Linux options, so there's no home server to maintain. Compare storage costs, encryption, Linux setup, and how long deleted files or older versions can be recovered before choosing.

Syncthing is another option if you mainly want folders shared between your own devices rather than stored with a cloud provider. It syncs between devices, so at least one other device needs to have a copy when you need it.

Pair it with a separate backup if you want protection from mistakes. Syncing a deletion isn't the same thing as keeping an older copy safe.

A local setup is possible too. An old laptop or inexpensive used computer could act as storage, with Nextcloud for syncing and a separate backup tool such as Borg for backups. That's more setup and maintenance than a hosted service, though, so it may not be what you're looking for.