Compiles, can get ingame, uses Mixins to work around missing Fork Hooks for structures and custom dimensions.

src/main/java/appeng/mixins/DimensionStructuresSettingsMixin.java

@@ -0,0 +1,36 @@
+package appeng.mixins;
+
+import appeng.worldgen.meteorite.MeteoriteStructure;
+import com.google.common.collect.ImmutableMap;
+import net.minecraft.world.gen.feature.structure.Structure;
+import net.minecraft.world.gen.settings.DimensionStructuresSettings;
+import net.minecraft.world.gen.settings.StructureSeparationSettings;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Mutable;
+import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+/**
+ * This Mixin will add the structure placement configuration for the meteorite structure
+ * to the static final immutable map that contains them. There is currently no
+ * Forge hook for this, and registering them during the registry event is already too late.
+ * <p>
+ * If this is not done, Meteorites spawn every chunk, since that is the default for missing entries.
+ */
+@Mixin(DimensionStructuresSettings.class)
+public class DimensionStructuresSettingsMixin {
+
+    @Shadow
+    @Mutable
+    private static ImmutableMap<Structure<?>, StructureSeparationSettings> field_236191_b_;
+
+    @Inject(method = "<clinit>", at = @At("TAIL"))
+    private static void addMeteoriteSpreadConfig(CallbackInfo ci) {
+        field_236191_b_ = ImmutableMap.<Structure<?>, StructureSeparationSettings>builder()
+                .putAll(field_236191_b_)
+                .put(MeteoriteStructure.INSTANCE, new StructureSeparationSettings(32, 8, 124895654)).build();
+    }
+
+}

src/main/java/appeng/mixins/DimensionTypeMixin.java

@@ -11,7 +11,7 @@ import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
 
 import java.util.OptionalLong;
 
-@Mixin(DimensionType.class)
+@Mixin(value = DimensionType.class)
 public class DimensionTypeMixin {
 
     @Inject(method = "func_236027_a_", at = @At("TAIL"))

src/main/java/appeng/mixins/SkyPropertiesMixin.java

@@ -14,7 +14,7 @@ import java.util.Optional;
 @Mixin(DimensionRenderInfo.class)
 public class SkyPropertiesMixin {
 
-    @Inject(method = "func_239215_a_", at = @At("HEAD"), cancellable = true, remap = false)
+    @Inject(method = "func_239215_a_", at = @At("HEAD"), cancellable = true)
     private static void byDimensionType(Optional<RegistryKey<DimensionType>> optional,
             CallbackInfoReturnable<DimensionRenderInfo> ci) {
         if (optional.orElse(null) == SpatialDimensionManager.STORAGE_DIMENSION_TYPE) {

src/main/java/appeng/mixins/SkyRenderMixin.java

@@ -11,16 +11,16 @@ import org.spongepowered.asm.mixin.injection.At;
 import org.spongepowered.asm.mixin.injection.Inject;
 import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
 
-@Mixin(WorldRenderer.class)
+@Mixin(value = WorldRenderer.class)
 public class SkyRenderMixin {
 
-    @Shadow(aliases = {"mc"})
-    private Minecraft client;
+    @Shadow
+    private Minecraft mc;
 
     @SuppressWarnings("ConstantConditions")
-    @Inject(method = "renderSky", at = @At("HEAD"), cancellable = true)
+    @Inject(method = "renderSky(Lcom/mojang/blaze3d/matrix/MatrixStack;F)V", at = @At("HEAD"), cancellable = true)
     public void renderSky(MatrixStack matrices, float tickDelta, CallbackInfo ci) {
-        if (client.world.func_234922_V_() == SpatialDimensionManager.STORAGE_DIMENSION_TYPE) {
+        if (mc.world.func_234922_V_() == SpatialDimensionManager.STORAGE_DIMENSION_TYPE) {
             SpatialSkyRender.getInstance().render(matrices);
             ci.cancel();
         }

src/main/java/appeng/mixins/StructureAccessor.java

@@ -0,0 +1,16 @@
+package appeng.mixins;
+
+import net.minecraft.world.gen.GenerationStage;
+import net.minecraft.world.gen.feature.structure.Structure;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.gen.Invoker;
+
+@Mixin(Structure.class)
+public interface StructureAccessor {
+
+    @Invoker("func_236394_a_")
+    static <F extends Structure<?>> F register(String id, F feature, GenerationStage.Decoration defaultStage) {
+        throw new AssertionError();
+    }
+
+}

src/main/java/appeng/mixins/TntAccessor.java

@@ -1,20 +0,0 @@
-package appeng.mixins;
-
-import net.minecraft.block.TNTBlock;
-import net.minecraft.entity.LivingEntity;
-import net.minecraft.util.math.BlockPos;
-import net.minecraft.world.World;
-import org.spongepowered.asm.mixin.Mixin;
-import org.spongepowered.asm.mixin.gen.Invoker;
-
-import javax.annotation.Nullable;
-
-@Mixin(TNTBlock.class)
-public interface TntAccessor {
-
-    @Invoker
-    static void callPrimeTnt(World world, BlockPos pos, @Nullable LivingEntity igniter) {
-        throw new AssertionError("Mixin dummy");
-    }
-
-}