As of September 2017, Veeam does not support a native S3 interface for use when connecting to Wasabi. Veeam has indicated this capability is coming in Veeam 10.x (see https://www.veeam.com/blog/leverage-vtl-on-amazon-aws-object-storage-s3-glacier.html). Veeam customers should contact their Veeam representative for more info on this. Wasabi is a member of Veeam's partner program and will certify this new Veeam capability once it's available.
Another approach to using Veeam with Wasabi leverages an approach developed by another Wasabi tech alliance partner, CloudBerry Labs (see https://www.cloudberrylab.com/blog/how-to-store-veeam-backups-in-cloud-with-cloudberry-backup/). This approach has been successfully used by several Wasabi customers.