I wouldn't expect Xunity autotranslator to work with that BepInEx version from 2020.
I haven't touched CM3D2 in years but I think I had to manually update BepInEx, XUnity and possibly UnityInjector to get it working. iirc you have to correctly set the path for UnityInjector folder in the config when updating it manually.
Or you can stick with Sybaris 1 instead of BepInEx when installing LMMT. Sybaris might be more stable for CM3D2 though I didn't have any issues with BepInEx
If there's any demand for CM3D2 I'll update the instructions in the guide to get it working. The scope of the guide was to use it as an expansion for COM3D2 and not much else. I personally never played it.