I thought I had tested using a configured environment variable during the build - let me try that again. Its possible my ARG value didn’t match the environment variable name configured.
It worked! It was an issue with my ARG names not aligning with the alias I had created.
One small UX improvement - would be nice to indicate which application created / exported the environment variable in the list of environment variables. For example, with multiple services, this type of value is repeated:
QOVERY_APPLICATION_Z832AFE71_HOST_EXTERNAL
It’s hard to match up which of the applications in the environment it refers to without viewing the value, then comparing it to the URL of the service by clicking “Open” from the application summary page.
There is a small trick, if you put your mouse over the icon, you’ll get the name of the app. (I know it’s not obvious, and thanks for suggesting a better UX).