Does it have API parity with S3 ? On top of normal get/put S3 offers a retention policies and abilities to apply say a given header to a file or whole bucket
Reading that only makes Minio and Garage seem more similar. They are both single-binary, clustered, S3-compatible file storage solutions. They are both meant for self-hosting on consumer-grade hard drives, provide redundancy to deal with drive or node failures, and don't aim to implement the entire AWS S3 API surface.
Seaweed design goals / features: https://github.com/seaweedfs/seaweedfs
MinIO: https://min.io/docs/minio/linux/operations/concepts.html
Note Garage list of non goals specify priority features of Seaweed or MinIO, for example erasure coding.