John,
Thank you for reaching out! This particular deployment type was an experiment that did not continue past 10.5.1. I'm taking a look to see if we can get it removed from the listings.
That being said, this was rolled up into a different project that should be releasing soon (ArcGIS Enterprise on Kubernetes). This is quite a bit bigger than just an ArcGIS Server Image, but nevertheless should be interesting. Stay tuned for more updates on that!
Keep on keeping on!