I finally got round to looking up how to emulate amiibo on my jailbroken 3DS, as well as connect to others with StreetPass.
The amiibo emulator is called Wumiibo and it's almost easier to use than a genuine amiibo. All you do there is download the Wumiibo Helper CIA from the UniStore (you can search for "wumiibo" and find it), then once that downloads and installs, run it to download the Wumiibo software. There's some topsy-turvydom you might need to do with Luma, insofar as enabling loading external modules, but that takes a minute to do and then you're done. You don't even need any of the amiibo BINs from No-Intro because Wumiibo is the reason why they exist and it already has a complete database of all the amiibo ever released. Including Rosalina... I seem to recall a single Tumblr user making a big deal out of that back in the day (holy shit, that day was 2015! 10 years of mariotehplumber's weird desire to corner the market on Rosalina amiibo... man...). Anyway, I've already summoned Resetti and Huck in New Leaf and Wario in Smash 3DS with Wumiibo. The instructions are all here and they're easy enough to understand as long as you've got your 3DS turned on so you can do stuff with it.
As for the StreetPass thing... we have to deal with a very poorly-documented service called Pretendo in order to emulate certain functions of the Nintendo Network. Right now, a Neocities mutual of mine and I are trying to troubleshoot it so we can appear in each other's Friend lists. For whatever reason, Pretendo (which uses a console-side manager app called "Nimbus") appears to allow you to link a Nintendo Network ID (NNID) or a Pretendo Network ID (PNID). Obviously, most everyone who had a 3DS from the olden days probably has a NNID, so your first impression is just to use it... but that functionality doesn't work and they don't plan to make it work. Why have the option? That's just bad software design at that point. Also, they don't make it clear enough whether you absolutely need a PNID or not. All they do is mention that the only time an NNID was absolutely necessary in history was in Nintendo Badge Arcade, which Pretendo isn't compatible with in the first place. But, they never expound upon certain key details that would streamline the procedure and result in the least wasted time chasing down errors.
At this stage, I'm mostly sure Pretendo is working because I received a SpotPass notification from them which sent me to StreetPass Mii Plaza to configure things. But, I won't be absolutely certain of anything until I can see another person's Mii in my Friend list. At least Wumiibo worked on the first go, so that's good anyway! Now I'm 1 step closer to furnishing my house in New Leaf like an office with a break room! Or a mall food court. Maybe the office for a few weeks, then the food court? Now I need to find out how to get the 7/11 stuff now that the SpotPass event has been over for 10 years. I'm assuming it's already in the game's files somewhere and it's just a matter of hacking. Why do I want the 7/11 stuff? Why wouldn't I want it? I quite fancy the idea of going back home to my very own convenience store every night. I can do it in The Sims, why not Animal Crossing, I ask you?