Good question.
I don't really understand features at all so all I can offer you is that in the line
addBiome("caelum_forest", Category.SWAMP, .15f, .8f, BiomeTemplate.DEFAULT_OVERWORLD_SKY_COLOR, BiomeTemplate.DEFAULT_OVERWORLD_FOG_COLOR, BiomeTemplate.DEFAULT_OVERWORLD_WATER_COLOR, BiomeTemplate.DEFAULT_OVERWORLD_WATER_FOG_COLOR, color(0,50, 70), color(0, 100, 150), GrassColorModifier.NONE, ParticleTypes.ENCHANT, .01f, 0f, .8f, new ConfiguredFeature<?, ?>[] {Features.field_243934_cq, features.get("test").get().withConfiguration(IFeatureConfig.NO_FEATURE_CONFIG) }, new StructureFeature<?,?>[] {StructureFeatures.field_244151_q});
".withConfiguration(IFeatureConfig.NO_FEATURE_CONFIG)" is underlined and it says "The method withConfiguration(capture#3-of ?) in the type Feature<capture#3-of ?> is not applicable for the arguments (NoFeatureConfig)."
If I cast features.get("test").get() as a Feature<NoFeatureConfig> the red line goes away but the game crashes on load with only the message "Mod Loading has failed" and points to the line that I pasted above
I don't even need help with this specifically, I just need a working example of features using deferred registries