I can help out a lot with this actually
At home I have several things for this including a video enabler for the emulator units without the video check that even comes with a couple extra options than standard.
As it turns out all the emulator units, except wireless & ds lite differences, were the same. The only differences were software locks by nintendo.
Anyways all i got is from some awesome people on this forum:
https://nsmbhd.net/forum/... in a thread that i might dig up later.
There's also stuff like an ida table of the firmware and maybe the software iirc. Probably not that'd be copyright material so you may have to find that on your own online. I do remember it being out there though
You can load one game at a time if your re-encrypt the rom with ndstool and use the software for the nitro to load it in.
You can also play retail gba games on the unit with a work around the block in the nitro software, but afaik you still cant play any retail games on the unit sadly.
That port is just used for flashing the dev flash cards that were used with these units.
Anyways hope that heps, im at work atm but ill link the thread i learned all this from later.