I am inspired now to dump my databases and rsync the content on a schedule.
1. A hard drive in a fire safe.
2. An S3 bucket, mediated by Wasabi.
3. My friend's server that lives at his house half a continent away.
It would be nice to have a fourth location that's a physical hard-drive that lives outside of my house, but close enough to drive to for pick-up, but it would mean either paying for a safety deposit box as you mentioned, or hassling a friend once a week as I come to pick it up and deposit it.
I figure that if a disaster that takes out my house and someone across town at the same time, I probably won't be worrying about restoring data. Across continent would only be viable with a server like you mentioned essentially buddyCloud.
I urge you to reconsider this belief if you have the financial means. Life continues after natural disasters. I lived in a place that was devastated by a hurricane and many people's homes were destroyed. Those people still live and work today, and they still needed their files. They especially needed their insurance documents after the hurricane.