Can just try to use aws configure and put in random values because sometimes server won’t check authentication.

To list buckets, use
aws --endpoint=http://s3.domain s3 ls.

To list all objects and prefixes for the buckets, use
aws --endpoint=http://s3.domain s3 ls s3://bucketname.

To download/upload the file (can upload shell if front end visible), use
aws --endpoint=http://s3.domain s3 cp s3://bucketname/filename filenametobesavedtolocal or vice versa if want to upload.