Emulators
Also heavily depends on the platform. Example PS2: Emulators are banned for pretty much every game.
the sticky in this very subforum: "creating a list of valid emulators" ... I guess that's answering your question?
It depends which game, for some consoles, emulators are completely banned but for certain games, emulators are allowed, they can sometimes be hidden off the main leaderboard however, like with later Pokemon games for example. It's best to research the game you're looking at and find out :)
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