See also: the directory https://github.com/relink2013/Awesome-Self-hosting-for-the-w..., that collects "self-hostable services with native mobile app clients." This project should be on there! (Right now, the only entries in the Photos category are two [closed-source!] Synology offerings, and one other app that's not E2E-encrypted. You're better than these — go claim your crown.)