It’s a bit hacky but I suppose there’s always the option of using a separate WebDAV server on the directory where frappe drive stores its files. I haven’t tried something like that, though. Unfortunately I don’t know of any integration within frappe drive itself. Seems they’re accepting contributions now so it’s possible these will be implemented in the future. WebDAV is a bit of its own beast, though, so that’ll be a huge undertaking in my opinion.
But then who backs up the backups?