UPDATE:
The QMJ current spec requires multiple changes, I'll give a PR which fixes them The other change to support QMJ was already implemented in 4.1.5

Describe the bug
Quilt Loader doesn't yet support hashed mappings, so the intermediate_mappings field in quilt_loader must be set to net.fabricmc:intermediary for Quilt to not throw a fit

To Reproduce
Steps to reproduce the behavior:

1. Use a Quilt Loader 0.16.0 beta instance with NEC Fabric in the mods folder
2. Attempt to launch the game

Stacktrace
Important line:

ParseException: Oh no! This version of Quilt Loader doesn't support hashed mappings, please update Quilt Loader to use this mod.