We are going through the exercise of experimenting with using the "all on one Machine" Cloud Formation template for ArcGIS Enterprise.
We found the following page has an old link at step 3 that is only up to date to 10.6.
The link on this page should be to
CloudFormation templates to deploy ArcGIS Enterprise on Amazon Web Services | ArcGIS Enterprise
We needed to do a fair bit of investigative work - traw;lingt hrough S3 buckets to work this out,
Hopefully, this will be corrected promptly
it seems it did get fixed
There is a lot of change in ArcGIS 10.8.1, haven't dig further, but it looks like the script works.