Sup. Quick post to make people aware that you can do coop online with friends reasonably easily.

Dolphin has built-in netplay functionality which should work well enough assuming you follow the setup instructions correctly.

If you want something easier to set up (and doesn't require the other player to have the game) you can also do the same using Nvidia Gamestream. This is an experimental feature for newer nvidia graphics cards so you simply enable that, boot dolphin and send your partner a link and they should be playing with you immediately.

Here's an example of an IL I did with a friend using Gamestream: This also depends on your internet connection heavily. While this is completely playable for us, keep in mind that we both have good internet speeds and only live a couple of miles apart.

This will work with whatever emulator of your choice, I don't suggest using PCSX2 for runs as it crashes at seemingly random during gameplay and the stable builds do not support the game's black outline on anything.