Way back when there was a proof of concept thing that ran I think it was the NES at 1fps or something ridiculous at one point.
In terms of anything vaguely usable, even attempting to emulate what was even then absolutely ancient machines. Not really. Specs wise you might be able to do something like CHIP-8 (indeed a token search says someone went there
https://github.com/elseyf/gb8 ), possibly a commodore PET, and you might be able to slap some form of BASIC interpreter hard enough to do something that counts as emulation of a sort as well but nobody has yet done them and I don't really expect anything outside of some people having a bit of fun for a kind of tech demo.