I have an idea, that may just be stupid enough to work.
Would it be possible to mirror the sites used for Browserhax on a local network, disconnect the actual internet from your router, and navigate to the local web page on the 3DS browser?
My thoughts for this working is that the WLAN switch is on, and connected to an SSID, so the 3DS shouldn't complain about it. Meanwhile, since it's not actually connected to the internet, shouldn't that bypass the "phone home" FW check for 9.9 <-> 10.3 users?
Would it be possible to mirror the sites used for Browserhax on a local network, disconnect the actual internet from your router, and navigate to the local web page on the 3DS browser?
My thoughts for this working is that the WLAN switch is on, and connected to an SSID, so the 3DS shouldn't complain about it. Meanwhile, since it's not actually connected to the internet, shouldn't that bypass the "phone home" FW check for 9.9 <-> 10.3 users?