Had great experience with garage for an easy to setup distributed s3 cluster for home lab use (connecting a bunch of labs run by friends in a shared cluster via tailscale/headscale). They offer a "eventual consistency" mode (consistency_mode = dangerous is the setting, so perhaps don't use it for your 7-nines SaaS offering) where your local s3 node will happily accept (and quickly process) requests and it will then duplicate it to other servers later.

Overall great philosophy (target at self-hosting / independence) and clear and easy maintenance, not doing anything fancy, easy to understand architecture and design / operation instructions.