https://github.com/jellysquid3/Lithium

I'm trying to connect to 2b2tpvp.net (1.12.2), but if I have Lithium loaded, Minecraft absolutely craps the bed attempting to connect, throwing the same error until I force close the game.

https://paste.dimdev.org/olicudirib.mccrash

Yes, if you want to use Lithium with this mod, you're on your own. Lithium messes with too much random stuff, and given that it's a server mod (hence only useful in singleplayer) I don't really want to officially support it. Try turning off different Lithium settings until it works.

@Mhowser If your still wishing to do this, use the following config:

lithium.txt
Ensure you rename the file to lithium.toml and replace the existing lithium config with this

For future reference, it is now lithium.properties and not toml

Reopening as I've decided on being compatible with lithium.

Lithium settings known to be incompatible with multiconnect so far:

• mixin.entity.data_tracker.use_arrays

Try version 1.3.6