When using the latest 1.21.1 Jenkins release of Quark it seems that the Quark animal variants cause a crash when combined with Nomansland:

• Latest.log: https://mclo.gs/N9dwmRl
• Crash Report: https://mclo.gs/LCfZ0JF

Nomansland uses the mixed_litter library for variants and until Quark was added the animals loaded fine, hence the issue report here :3.
It might be an idea just to force disable Quark animal variants if the mixed_litter library or Nomansland mod is found or something.

Ok so disabling the mob variants doesn't actually do anything it still crashes unfortunately.