I'm running a Nextcloud instance (which uses WEBDAV for uploads/downloads) on an old fanless PC next to me, attached to a 14tb drive I picked up at a steal. Because I'm too lazy to actually write a backup script and handle Amazon Deep Freeze or whatever the fuck it is, I have a subscription to Crashplan, which backs up everything to their cloud however often I'd like it to. Now, if you want to go simpler, just get a SMB share set up on a Linux box, then do the same thing with Crashplan backing up the targeted folder.