This still exists actually and anyone can do it with most Raspberry Pis (Raspberry Pi 2B+ to 4B according to
the official website for the software, I would believe 5 models would work fine but YMMV) and a GPIO board with buttons.
You can buy a (overpriced) pre-made box of it or just get a look at what Merki's GPIO board looks like
here.
Only works with New 3DS models using Katsukity's 2nd generation capture card (according to Merki, I had no idea there was even a 1st and 2nd generation of the capture card)
Software for the Raspberry Pi
Readme has to be translated, you can just throw it into Google Translate or parts of it into DeepL.
Info/FAQ on the (TV-Kit) software written by Merki
You can watch about the (TV-Kit) software here
For OP
@PopPunkGameTime or anyone else who would want to make their own "TV-Kit",
Your best chance at being able to actually use it is only if you
- have a New 3DS/2DS with one these "2nd gen" Katsu boards already
- or buy one of the Katsu boards from here. (Optimize is the official manufacture for Katsukity's boards) and do a self-install if you have the micro-soldering skills and knowledge. They are only selling New 3DS XL kits at the time of writing this
- or buy a New 2DS XL from Merki or contact them (scroll down to find contact info and form, they also have a Discord) see if they are willing to do a install for one of the boards
- or find a pre-installed or installer/seller on Twitter, eBay and possibly Etsy (eBay and Etsy will most likely be insanely expensive for installs and pre-installed models. Etsy has a lot of "wireless capture card" install listings that are just custom firmware mods)
- or if you can't find anyone currently installing Katsukity (not Loopy!) capture boards, find a experienced and trustworthy modder who's done work on Switch modchips on here or other social media platforms (r/SwitchPi****s has a lot of them on there) and risk it all if they are willing to take a stab at it and share these instructions with them (These boards are NOT, at ALL, easy to install whatsoever. You need someone who who is experienced in microsoldering and shell cutting, ModvilleUSA called the New 3DS XL kit the hardest mod kit he's ever installed)
Current installers I could find at the time of writing this:
- DelfinoCustoms is more then likely your best bet. Their send-in services appear to be in backorder but they do in-fact use Katsukity boards. They are located overseas but their website will show USD prices and provide shipping information for send-in services.
- RubyOtakuMods located in the EU (apparently take international orders from a Reddit comment I found), but they seem to be filled up on orders at the time of writing this. No idea if they do Katsu boards, might only be for Loopy boards.
- 3DSCaptureZ is located in France, no idea if they do overseas commissions, but they are currently looking to switch to batches of installations because of some issues their having with installs and having to reimburse customers. Maybe take a look at them in the future.
- ModsvilleUSA might be willing to install it but as I showed in the video I linked I would assume he's likely going to want a real pretty penny or just flat out not be willing.
If anyone else know any other modders feel free to reply to me with them, especially if they are in the US.