The old thread made back in march is out of date. If your on 3.0.0 block these addresses (eshop access won't work, until someone figures out a bypass)
here is the complete list of must blocks
ones known previously:
http://sun.hac.lp1.d4c.nintendo.net:443
http://beach.hac.lp1.eshop.nintendo.net:443
and ones that I found (that you must block to stop update nag! as of august):
http://dauth-lp1.ndas.srv.nintendo.net:443
http://atumn.hac.lp1.d4c.nintendo.net:443
http://aqua.hac.lp1.d4c.nintendo.net:443
you must block all five as of august in order to stop switch nag.
Some useful threads
Fiddler guide
https://gbatemp.net/threads/tutorial-fiddler-setup-guide-for-blocking-update-server.466328/
out of date list (but contains stuff not mentioned!)
https://gbatemp.net/threads/dns-to-block-the-updates-of-the-switch.465952/#post-7208328
Eshop problem:so as far as I looked into it (not super deep) it appears dauth is responsible for allowing people into eshop.... but there is a catch. as that also make the system nag for a update.... So this means that somebody has to figure out a tool to force the response to duath to be different or valid. aqua is also the same... As far as I know. Which I'm not the smartest guy on the planet so I could be partially wrong. However I can confirm that all five must be blocked.