This method will still allow you to use online features.
I did testing on all games and online features worked.
This is for temporary use till atmosphere and switchbrew codes are updated to work on newest firmware versions.
The online games may force you to update at later time.
you need to add this in default.txt in the hosts folder in atmosphere folder on your SD card.
#block nintendo updates
127.0.0.1 receive-%.dg.srv.nintendo.net receive-%.er.srv.nintendo.net
sun.hac.%.d4c.nintendo.net
atumn.hac.%.d4c.nintendo.net
127.0.0.1 sun.hac.lp1.d4c.nintendo.net
127.0.0.1 atumn.hac.lp1.d4c.nintendo.net
then make sure you enable dns mitm
add those in your system_settings.ini in folder config in your atmosphere folder on your SD card.
[atmosphere]
enable_dns_mitm = u8!0x1
enable_dns_mitm_debug_log = u8!0x1
Thanks and Credit to: https://github.com/kinnay/NintendoClients/wiki/Server-List