The JPN New3DSes have content filtering that is extremely restrictive, to the point where it blocks Spotify because it is "streaming: music". (I wonder what kind of mature content I can find there 👀). In order to remove the content filter, Nintendo required that you pay a tiny amount of money via credit card. But now? You can't remove it at all, because they've stopped supporting credit cards on the eShop. So, here's a GodMode9 script to toggle the content filter.
Both _en.gm9 and _ja.gm9 do the same thing, but messages in _en.gm9 are in English and those in _ja.gm9 are in Katakana.
_en.gm9: GodMode9 v1.9.2pre1 or above. _ja.gm9: GodMode9 v2.1.0 or above.
You must have opened the browser at least once before using this script so that the savedata exists to modify.
Public Domain (Unlicense)
For more details, see LICENSE.
The script modifies a certain part of the browser's savedata.
Although I have confirmed it did disable and enable the filtering without visible trace of detection by the browser, I cannot assertively deny the possibility that the browser is aware of it, or that a future version of the browser can detect it.
Please use this script at your own risk.