Yep. There's multiple alternatives. When/if they're appropriate as a drop-in for Minio and (for packagers) as an extension, there's more than one path. Looking only at things that seem to be "live"/viable:
Service
URL
License
Notes
Garage
https://garagehq.deuxfleurs.fr/
GNU AGPL
EU-based, compatible with many common clients, might serve as a static site/fileserver as well
SeaweedFS
https://github.com/seaweedfs/seaweedfs
Apache 2.0
Can run as a single binary; can grow its storage area by adding to a list of paths (which would play well with Cloudron's volume mount model)
VersityGW
https://github.com/versity/versitygw
Apache 2.0
Essentially proxies S3 straight to the filesystem, allowing access to files either through the S3 API or directly through the underlying filesystem. (Sounds easy to backup.)
RustFS
https://github.com/rustfs/rustfs
Apache 2.0
Explicitly supports a single disk/single node deployment, but it looks like it wants direct access to disk mounts.
Ozone
https://github.com/apache/ozone
Apache 2.0
Apache Foundation object store project. Handles HDFS and intended to scale. Not really appropriate for Cloudron's use-case.
Garage and/or Seaweed are likely the most mature of this bunch. Versity might be the simplest.
the start of a package
After looking at the Garage repo, it was apparent that it should be very packageable. All the right things are broken out as environment variables.
https://git.jadud.com/jadudm/cloudron-garage
I was able to:
Push this to a private registry I'm hosting on my Cloudron
Use the cloudron build and cloudron update sequence to make changes and improve it on my Cloudron instance
Use the terminal to create a zone/location, assign it some space, and create a bucket
Create a key for that bucket
Use mc (minio client) to put a file in the bucket and list the contents of the bucket
There's a bunch more that would need to be done. A few thoughts, mostly random:
The SQLite metadata needs to be backed up correctly. It might be that I've already done everything necessary by using localstorage and pointing it at that metadata DB.
I used httpPorts to map almost all of the endpoints that are supposed to be public, but... I'm not sure I wired everything up correctly in the config. Something was right (since I could use the API), but I did not test (say) the admin API, and I did not expose the K/V database API. (Which... could be handy to expose.)
The docs say httpPort is optional/not required, but the command line tools disagree. The docs should be updated.
I didn't try and play with SSO, but I don't know if I have to? Or, there's a bunch to think about there. I think garage is kinda secure out-of-the-box (with no keys configured by default, etc.), but that doesn't mean I'm confident. As a result, perhaps SSO isn't necessary?
I did not experiment with exposing anything as a web page. The notion that I could push to a bucket and use that as a static site server (as opposed to creating surfer instances, say) is compelling. But, I'd have to figure out how to map the domains...
If this is a direction things go, I'd be glad to be a sounding board/help out.