Dolphin Progress May and June 2020
Slightly related, a couple of weeks ago a guy named Fizzi released a dolphin build with rollback netcode support for Super Smash Bros Melee, making it a game with better netcode than most current big name fighters.The way he implemented it is insane, he had to reverse engineer a way to generate arbitrary game states in game, as using dolphin savestates was not performant enough.He's also added other amazing features, like in game matchmaking, or my favorite, being able to stream a game state through the Wiis ethernet port, so two players can be competing on original hardware while a stream setup upscales that footage in realtime to 16:9 4k through Dolphin, and also generates real time match stats, saves replays... Incredible stuff.Here's the project page: https://slippi.gg/ 
and a video from a top melee player showcasing the matchmaking: https://www.youtube.com/watch?v=erbZV8u6-hA