OP here. I thought this was quite interesting as it's built around the RP2040, using GPIO to communicate with the DS - the firmware is completely open source and reprogrammable via USB.

Additionally, the launcher supports a bunch existing flashcards all the way back to the original R4 which released in late 2006.

Also, it's cheap! Unsurprising given the hardware, but I picked up a couple for $10 each, compared to the $40-50 you'd pay back in the day