Update
Adam's statement
Our high availability solution is focused around centralized configuration using git with data storage in instance registration in SQL.
The idea is to stand up multiple PowerShell Universal instances and configure them to use the same central SQL server database. As the instances connect they will register with the job queue and will process jobs as they come in. Job data will be stored centrally in SQL. Additionally, app tokens and identities are stored centrally in SQL so that you can use the same app tokens and role-based access across the instances.
In terms of configuration, the PS1 files used to configure PSU, should be stored in a central git repository. In version 3.1, you can store the git configuration settings in SQL so that once the PSU instances connect, they will be able to retrieve the git repository information and pull their configurations. This ensures that all machines in the cluster are configured the same way.
In front of the cluster, you will need a load balancer or other fail over application to redirect traffic to the individual instances. The gateway needs to support sticky sessions in order to support dashboards. Additionally, PSU takes advantage of web sockets heavily and it is a requirement that the gateway or load balancer support forwarding web socket connections.