Whenever I start up a server with both MCMT and Lithium installed, I get this error:
https://pastebin.com/P1sChZvd

There is already an issue posted on the MCMT repo, and in the comments, a contributor stated that Lithium is overwriting a function which makes it fail: himekifee/MCMTFabric#1. I would love to see this mod be compatible with MCMT as that would improve the performance of a server much.

try mixin.world.chunk_access=false in the config