Quilt Loader does a terrible job of handing solver errors outside basic missing dependencies right now. This usually happens when mods declare themselves as incompatible with each other, but other things can cause it too.
If you're having trouble reading an unhandled solver error, ask for help on our forum or Discord server! You will get much faster and better support than here on GitHub.

Example with images and crash log: #295

#305 exists to start work on improving this. For now, we'll just have to suffer together!