Yepp! exosphere.ini can be used for both. Atmosphere always read it before "booting" your respective nand. very simplifed.
https://switch.hacked.us/extras/incognito/
blank_prodinfo_sysmmc=0
blank_prodinfo_emummc=1
here is an example lets say you play online with bought games on sysnand. Sysnand isn't blanked out and works like a normal Switch.
But prodinfo is blanked on emunand and therefore it won't be able to connect to nintendo online. Plus it's "blanked" so nothing to ban.
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You can even setup MITM blocklist with Atmosphere to do a "local" 90dns.
Download this - https://nh-server.github.io/switch-guide/files/emummc.txt
It will ONLY block Nintendo on Emunand.
https://nh-server.github.io/switch-guide/extras/blocking_nintendo/ - how to set it up.
