I’ve been seeing articles showing off new handheld hardware that looks like a GameBoy, but presumably are emulators. Where do people get games for those?
Sometimes the maker of the game offers a ROM for download, either for purchase or for free. There are USB devices that'll dump a ROM cartridge, such as the Retrode.
Presumably they just download the original ROMs which are incredibly easy to get just by searching "gameboy ROMs". Because they are so incredibly small in filesize they are hosted pretty much everywhere. People share still photos with each other that are larger than most of those games.
iirc most of these type of things come preloaded with all of the games up to GBA or so, the entire library is tiny by today's standards, I download ML models bigger than like... all games made prior to 2000 on a regular basis