OptiFine & Shaders - mahjerion/Craft-to-Exile-Dissonance GitHub Wiki
OptiFine is not officially supported by Craft to Exile [Dissonance]. However, members of the community (special thanks to Occultos) have worked hard to find working versions. It'd be wasteful to not share them here! USE AT YOUR OWN RISK! It's known that you will have visual artifacts, and in some cases, items may appear invisible!
Without Shaders
Use Optiforge-MC1.15.2-0.1.33 with OptiFine 1.15.2 HD U G6. If it doesn't work you can try other OptiFine version until it does, I guess.
With Shaders
You do not want OptiForge. Use Preview OptiFine 1.15.2 HD G1 pre18 and Sildur's Vibrant shaders v1.283 Extreme-Volumetric lighting. You can find these files pinned in #dissonance-general on the Discord server.
Don't bother with other combinations, extensive testing has been done and this is literally the best OptiFine version and shader for Craft to Exile [Dissonance] with minimal issues.
Note that some of this info may be outdated. You might need to fiddle around with version until you get one that works.