I want to play with some people I met on discord, But I don't want to give them my IP For port forwarding, Is there any other way to play with them?.
IP Addresses are public information, so I wouldn't worry about giving it out.
You can also join an empty server together and play on that.
@UsernameIsTaken https://forum.plutonium.pw/topic/7/custom-games-with-friends explains a way using upnp that CAN work, if it doesn't you're gonna have to forward the port.
If the people in your match really wanna get your ip tho they can, no way around that as they connect directly to your client.