If you start Lithium on Fabric with OptiFabric, even before starting the game, a 'Failed to Launch' screen will appear.
I intend to use both at the same time, since lithium helps a lot in FPS and Optifine makes it possible to use shaders, but even using previous versions of both, none of them seem compatible.
NOTE: In Sodium the same problem occurs with OptiFabric.

Lithium is purposefully made to disallow loading with optifine due to compatibility issues in the past. Duplicate of #73