I'm aware that Pretendo exists, but I don't know if it's active enough to get into a full 8-player match at any time, I'm guessing it probably has to rely on Discord matchmaking.

I also feel like it needs to be said that S1's balance is not good, and I'll bet anyone still playing it today knows how to run circles around a casual beginner. It's not like you'll be getting any kind of skill-based matchmaking here.