I've got an anbernic RG351 and it runs everything from early N64 an older flawlessly, good battery life, decent screen and fairly good buttons, really good if you're out and about because it's nice and compact. I've also got a Steam Deck that does everything else and as a home console.
Even better just get a cheap smartphone and one of those controllers that snap on the back like the kishi or whatever. My very mid range phone runs anything up to 3DS smoothly.