Have you tried Itch.io? They have a lot of Gameboy and NES roms that are “Name your own price.” I don’t have any recommendations - I’ve just started poking around with homebrew roms myself.

• https://itch.io/games/top-rated/downloadable/free/tag-nes-rom
• https://itch.io/games/top-rated/downloadable/free/tag-gameboy-rom

Nintendo Switch cartridge based games have a file that’s unique to each individual cartridge. The dumper and accompanying flash cart make use of that file. If Nintendo detects two people playing while connected to the internet with the “same” cartridge, there’s a high chance of them banning both consoles. So any used game anyone buys after this point runs the risk that someone dumped it, maybe an old owner who resold, maybe someone who bought and returned it, etc, which means even a legitimate user who hasn’t even heard of the flash cart could get banned. There’s also the potential issue of people using the tech in the flash cart once people figure out how to use those chips to sell bootlegged reproduction cartridges that have the same issue

Oh wow, so they’ve poisoned the used market for Switch games. That’s disappointing.

ContraPoints has a video that explains a lot of it: https://youtu.be/7gDKbT_l2us?si=_RQR_ZJE2ZHsh8E2

What’s galling is that big companies claim that the main reason for making people come into the office is to promote in-person collaboration. But, they constantly demonstrate that they don’t, in fact, value in-person collaboration. They organize people into cross-geography teams all the time to save money on hiring. So, you’re often sitting in a cubicle on a conference call with people on the other side of the planet that you will never see in the hallway. Or worse, you’re sitting in a conference room with a handful of coworkers, struggling to communicate over a crappy speaker phone with a handful of coworkers on the other side of the planet. They also frequently lay off entire product teams in one fell swoop. Decades of institutional knowledge that you might tap into during a water cooler conversation just disappears overnight. It’s hard to go along with all the extra real costs and pay the happiness tax that commutes and cubicle farms extract when it’s so obvious that the stated reason for it all is a lie.