I found this thread which is more than 2 years old and didn't actually provide a definitive answer:
https://thwack.solarwinds.com/product-forums/network-performance-monitor-npm/f/forum/89185/list-of-urls-needed-by-orion
Is there now a definitive list of URLs that the Orion Platform and individual modules "require" for operation?
The use case is an install in a very secure environment where the Orion pollers are likely to be locked down on internet access except to those required URLs.
Thanks.