To start things off: I play Hellish quart, a physics based sword fighting sim (that has remote play) so if anyone wants to engage in a sword fight hmu, once I add you on steam you won’t have to buy the game (my internet isn’t the best though, so depending on factors it might be laggy).
Yes, both Ryujinx and Yuzu can do multiplayer by emulating the Switch's wireless functionality, though Yuzu's servers have been shut off for obvious reasons. You can still play online on Yuzu through Hamachi or similar though.
Other emulators also have multiplayer, several PS2 multiplayer games are playable on PCSX2 with community servers and there's an entire Xbox Live replacement service for the original Xbox.