FYI the only core in Retroarch that was able to recognize and run the ROM is QuickNES. I suspect the rom is headerless.
I've tried all the three roms, and Retroarch didn't initially recognised them automatically scanning the folder. Then I've tried a manual scan of the folder setting a specific core association each time and I've tried the following cores in this order:
- FCEUmm
- Mesen
- Nestopia UE
- QuickNES
The first tree didn't recognize any of the roms, while QuickNES grabbed them all.
It's worth saying that once the roms were successfully added all the four cores were able to run all the roms, even the 128k one. Given that the roms are running flawlessly but were tricky to be recognised/validated (and that's the first time that happens me with any custom rom) I blamed the header, but the truth is that I'm not that technical with NES roms.
Another thing that is worth saying is that I'm using an M2 Mac, and afaik some of those cores have a build that is specific for M2 while some others are universal (that means that are used on both Intel and M Macs).
Any other standalone Mac emulator grabbed all the roms flawlessly.
That said, thanks a lot, the game is awesome <3