The nightmare continues. For now I am using 3rd party backup services that are (currently) promising me that my backups are encrypted by a key they do not have access to, or control over. But can this even be believed in an age where these secret notices are being served to any number of companies? I suppose the next step would be to ensure that files don't ever arrive in the cloud unencrypted, but I have yet to see…
IMO the only thing you can have a high level of trust in is your own *nix server. Backup those devices to it then encrypt there before being sent to the cloud.
Just be sure it's pre-Intel Management Engine / pre-AMD Platform Security Processor!