Currently, there is no easy way to redundantly backup a Bitwarden homeserver to the Bitwarden’s cloud servers. Having this option would prevent permanent loss of passwords in case one’s homeserver goes down.
(Other topics discuss local backups for homeservers, but this has its own pros and cons.)
I’m trying to understand the use-case here. I believe that most users who choose to self-host do so because they do not want to have to rely on the availability or security of Bitwarden’s cloud server. So if you do want Bitwarden to keep a cloud backup of your vault, then why bother with self-hosting at all?
If you don’t have local copies of your passwords on your mobile/desktop etc, or even if you do, them being in the same location as your server means natural disaster would destroy passwords forever. I realize now that I could self-host in an offsite data center to mitigate this.
Well, this is exactly the benefit that would be provided by using a Bitwarden-hosted vault, instead of a self-hosted server.
I still don’t understand why you wish to continue self-hosting, instead of just taking advantage of a service that is offered by Bitwarden (for free even!) to solve the exact problem you have described.
“Always” cannot be guaranteed, but I think that you will have fewer problems with Bitwarden’s servers going down than you will have with your own home server going down (which was the original reason that you made this thread).
And to reiterate what @Peter_H wrote: If somebody breaches Bitwarden’s servers (or if some Bitwarden employee goes rogue and tries to steal data), your passwords cannot be seen by the attacker — your secrets are safe, unless you have chosen a weak Master Password (which would expose you to a brute-force attack).