Thanks for the kind words.
The next update to the list will be posted Feb 27 with 100+ new servers added.
Yes, if you have additional addresses for USA-based government ArcGIS servers please send them my way.
I am looking for root addresses ending in "rest/services".
Contact page: https://mappingsupport.com/p2/gissurfer-about-contact.html
Despite my best efforts to explain the intent of my list, well meaning people keep sending me portal addresses. Sigh.
I will post a GeoNet 'document' later today. Good idea.