> weird to call it S3
I feel that is a bit of an unfair assessment.
AWS S3 was the first S3-compatible API provider, nowadays most cloud providers and bunch of self hosted software supports S3(-Compatible) APIs. Call it Object Store (which is a bit unspecific) or call it S3-Compatible.
EKS and EC2 on the other hand are a set of tools and services, operated by AWS for you - with some APIs surrounding them that are not replicated by any other party (at least for production use).
You can even do S3-on-ZFS
Which solutions do you find stable?
Wouldn't consider myself qualified to answer, but I'm not aware of any problems we had with our Oracle ZFS storage appliance.