I'm working on one that's cross-platform, and, critically, self-hosted. The beta is available for free in exchange for your feedback.

It's an early product, but I'm pushing out new features monthly. Face detection and sharing are coming soon. https://photostructure.com/faq/why-photostructure/

FWIW, I recommend to my beta users that they personally store at least one of their backup copies. https://photostructure.com/faq/how-do-i-safely-store-files/