The endpoint_url does not support IPv6 addresses.

[WangChangsongGit]

If endpoint_url is set to an IPv6 address, for example, [xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx]:9000, the S3 storage cannot be connected.

c.S3ContentsManager.endpoint_url = "[xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx]:9000"

[danielfrg]

I am happy to keep it open for reference until its fixed but I think you should create another issue on S3FS (https://github.com/fsspec/s3fs). I just pass that value to that library directly.