Yikes. Ran into a shortcoming of caddy-fs-s3: it requires a bucket to function.
With minio, I had every static site under sites/<host>, and this worked. Under Garage, I'm trying to move to <host>, and using local bucket aliases, but that doesn't work with caddy-fs-s3.
And I can't use Garage's website feature either, because that requires a global bucket alias, which is something I'd like to avoid.