It’s been pretty stable for the past few years. Most of the articles will be from 2015 or 2016, but not much has changed since then. We just hat another deployment 6 months ago, and it was the same routine as always.
Haven’t done a GovCloud installation myself, but we have one client in the sales pipeline that would require it. As I understand things, you’re on the right track in asking the question, as GovCloud is mostly similar to the HIPAA tier.
Keep in mind that HIPAA and GovCloud have always had a limited set of functions, and not supported things like Elastic Beanstalk and 3rd party logging and data storage. So not supporting Atlas is pretty standard in that regard.