https://nh-server.github.io/switch-guide/
After following that, you'll still need sig patches:
https://gbatemp.net/threads/latest-fs-and-acid-patches-for-kosmos.562915/
Download and extract both FS/ACID (hekate.zip) and ES patches to SD. Then you should remove the sysMMC entries from bootloader\hekate_ipl.ini for safety reasons.
You don't really need a second Switch. If you take the proper safety precautions, use emuNAND and keep your sysNAND clean for online use, it's like having two isolated systems.
https://raw.githubusercontent.com/Atmosphere-NX/Atmosphere/master/config_templates/exosphere.ini
Download this and place on the root of the SD card.
Change this line:
blank_prodinfo_emummc=0
to this:
blank_prodinfo_emummc=1
And that should make it safe to connect to wifi in emuNAND as it anonymizes the console. You won't be able to connect to Nintendo services while in emuNAND but you can install games over wifi and use homebrew that needs internet.
I still recommend also using 90DNS on emuNAND as that will actually block the connection.
https://gbatemp.net/threads/90dns-dns-server-for-blocking-all-nintendo-servers.516234/