Followup on this: Looking into Garage first. Very simplified access model, which is not necessarily a bad thing. Seems to work fine with #CloudNativePG (#CNPG). Can create buckets and keys through the API.
Considering putting the time to try write an operator for #Kubernetes that can request buckets from various providers, inspired by StorageClasses and PVCs. Throw a bucket claim manifest in your name space, and receive a secret with credentials for it. Apply to CNPG or Mastodon or whatnot, and Bob's your uncle. Easily request from different providers, either local or remote. I'm thinking MinIO, Garage and perhaps RustFS too. Multi tenancy safe too, somehow.