Look into Backblaze B2. Use rclone, or another backup tool that has S3 compatibility (though B2 API has some additional bells and whistles).

With rclone, you can also have a step to seamlessly encrypt the contents on the client side before sending to an external provider like B2.

I chose B2 because it is the most affordable option, but rclone supports many backends.

Rclone is a great tool but it is not really a complete backup tool. Ie no snapshots.

You can use it to sync local snapshots or to a destination that does snapshots for example

Borg/restic are more complete solutions